FIG. 2. - a, Feeler of Saturniid Moth (Telex Polyphemus), magnified 3 times. b, c, Tips of branches, highly magnified. maxillae are so re duced that they take no food in the imaginal state. The nature of the jaws has already been briefly described. Functional mandibles of peculiar form (fig. 3, A) are present in the remarkable small moths of the genus Micropteryx (or Eriocephala), and there are vestiges of these jaws in other moths of low type, but the minute structures in the higher Lepidoptera that were formerly described as mandibles are now believed to belong to the labrum, the true mandibles being perhaps represented by rounded prominences, not articulated with the head-capsule. Throughout the order, as a whole, the jaws are adapted for sucking liquid food, and the suctorial proboscis (often erroneously called a g " tongue ") is formed as was shown by J. C. Savigny in 1816 by two elongated and flexible outgrowths of the first maxillae, usually regarded as representing the outer lobes or galeae (fig. 4, A, B, g). These structures are grooved along their inner faces and by means of a series of interlocking hair-like bristles can be & joined together so as to form a tubular sucker (fig. 4, C). At their extremities they are beset with clublike sense-organs, whose apparent function is that of taste. The proboscis when in use is stretched out in front of the head and inserted into the corolla of a flower or elsewhere, for the absorption of liquid nourishment. When at rest, the proboscis is rolled up into a close spiral beneath the head and between the labial palps (fig. 4, A, p). Only in the genus Micropteryx mentioned above is the lacinia of the maxilla (as A. Walter has shown) developed (fig. 3, B, c). The maxillary palp is usually a mere vestige (fig. 4, B, p) though it is conspicuous in a few families of small moths. A consider Afte r A. Walter (Jen. Zeits. f, C FIG. 4. - Arrangement of the jaws in a typical Moth. Somewhat diagrammatic and in part after E. Burgess and V. L. Kellogg (Amer. Nat. xiv. xxix.).
A, Front view of head.
m, Vestigial mandible.
C, Part transverse section showing how the channel (A) of the proboscis is formed by the interlocking of the grooved inner faces of the flexible maxillae.
n, Nerve.
FIG. 5. - Wing-neuration of a Notodont Moth. 2, Subcostal; 3, radial; 4, median; 5, cubital; 7, 8, anal nervures. a, Discoidal areolet or " cell "; f, frenulum. Note that the forewing has five branches (1-5) of the radial nervure, the hindwing one only. The first anal nervure (No. 6) is absent.
hindwing subserves the same function. In the most primitive moths a small lobate outgrowth - the jugum (fig. 6, j.) - from the dorsum of the forewing is present, but it can be of little service in keeping the two wings together. A jugum may be also present on the hindwing. The legs, which are generally used for clinging rather than for walking, have five-segmented feet and are covered with scales. In some families the front pair are reduced and without tarsal segments.
Ten abdominal segments are recognizable in many Lepidoptera, but the terminal segments are reduced or modified to form external organs of reproduction. In the male, according to the interpretation of C. Pey 3 toureau, the lateral plates belonging to the ninth seg ment form paired claspers beset with harpes, or series of ridges or teeth, while the tergum of the tenth segment forms a dorsal hook - the uncus - and its sternum a ventral process or scaphium. In the female the terminal segments form, in some cases, a protrusible ovipositor, but the typical hexapodan ovipositor with its three pairs of processes is undeveloped in the Lepidoptera.
As already mentioned, the characteristic scales on the wings, legs and body of the Lepidoptera are cuticular structures. A complete series of transitional forms can be traced between the most elaborate flattened scales (fig. 7, B) with numerous longitudinal striae and a simple arthropod " hair." Either a " ` hair " or a scale owes its origin to a special cell of the ectoderm (hypodermis), a process from which grows through the general cuticle and forms around itself the substance of the cuticular appendage. The scales on the wings are arranged in regular rows (fig. 7, A), and the general cuticle is drawn out into a narrow neck or collar around the base of each scale. The scales can be easily rubbed from the surface of the wing, and the series of collars in which the scales rest are then evident (fig. 7, A, c) on the wing-membrane. On the wings of many male butterflies there are specially modified scales - the androconia (fig. 7, C) - which are formed by glandular cells and diffuse a scented secretion. In some cases, the androconia are mixed among the ordinary scales; in others they are associated into conspicuous " brands " (see fig. 66). The admirable colours of the wings of the Lepidoptera are due partly to pigment in the scales - as in the ease of yellows, browns, reds and blacks - partly to " interference " effects from the fine striae on the scales - as with the blues, purples and greens.
A few points of interest in the in- " n ternal structure of the Lepidoptera deserve mention. The mouth opens into a sub-globular, muscular pharynx which is believed to suck the liquid food through the proboscis, and force it along the slender gullet into a croplike enlargement or diverticulum of the fore-gut known as a " food-reservoir " or " sucking-stomach." The true stomach is tubular, anu beyond it lies the intestine into which open the three pairs of excretory (Malpighian) tubes. The terminal part of the intestine is of wide diameter, and in some cases gives off a short caecum. The brain and the sub-oesophageal ganglia are closely approximated; there are two or three thoracic and four (rarely five) abdominal ganglia. In the female each ovary has four ovarian tubes, in which the large egg-cells are enclosed in follicles and associated with nutritive cells. There is a special bursa which in the Hepialidae opens with the vagina on the eighth abdominal sternum. In the Micropterygidae, Eriocraniidae and the lower Tineides, the duct of the bursa leads into the vagina, which still opens on the eighth sternum. But in most Lepidoptera, the bursa opens by a vestibule on the eighth sternum, distinct from the vagina, whose opening shifts back to the ninth, the duct of the bursa being connected with the vagina by a canal which opens opposite to the spermatheca. In the male, the two testes are usually fused into a single mass, and a pair of tubular accessory glands open into the vasa deferentia or into the ejaculatory duct. In a few families - the Hepialidae and Saturniidae for example - the testes retain the primitive paired arrangement. These details have been worked out by various students, among whom W. H. Jackson and W. Petersen deserve special mention. Summing up the developmental history of the genital ducts, Jackson remarks that there is " an Ephemeridal stage, which ends towards the close of larval life, an Orthopteran stage, indicated during the quiescent period preceding pupation, and a Lepidopteran stage which begins with the commencement of pupal life." Development - Many observations have been made on the embryology of the Lepidoptera; for some of the more important FIG. 8 A. - Cossus macmurtrei. r (MacMurtrie's Goat Moth.) N. America.
results of these see Hexapoda. The post-embryonic development of Lepidoptera is more familiar, perhaps, than that of any other group of animals. The egg shows great variation in its outward form, the outer envelope or chorion being in some families globular, in others flattened, in others again erect and sub-conical or cylindrical; while its surface often exhibits a beautifully regular series of ribs and furrows. Throughout the order the larva is of the form known as the caterpillar (fig. i, a, b, fig. 8 B) FIG. 8 B. - Larva of Cossus cossus. (Goat Moth.) Europe.
characterized by the presence of three pairs of jointed and clawed legs on the thorax and a variable number of pairs of abdominal " prolegs " - sub-cylindrical outgrowths of the abdominal segments, provided with a complete or incomplete circle of hooklets at the extremity.
There are ten abdominal segments - the ninth often small and concealed; prolegs are usually present on the third, fourth, fifth, sixth and tenth of these segments. The head of the caterpillar (fig. 9) is large with firmly chitinized cuticle; it carries usually twelve simple eyes or ocelli, a pair of short feelers (fig. 9 At) and a pair of strong mandibles (fig. 9, Mn), for the caterpillar feeds by biting leaves or other planttissues. The first maxillae, so highly developed in the imago, are in the larva small and inconspicuous appendages, each bearing two short jointed processes, - the galea and the palp (fig. 9, Mx). The second maxillae form a plate-like labium on whose surface projects the spinneret which is usually regarded as a modified hypopharynx (fig. 9, FIG. 9. - Head of Goat Moth Lm). The silk-glands whose ducts Caterpillar (Cossus) from beopen on this spinneret are paired hind. Magnified. (From Miall convoluted tubes lying alongside and Denny after 14yonnet.) the elongate cylindrical stomach. At, Feeler.
body of the caterpillar. They are re- Lm, Second maxillae (Labgarded as modified salivary glands, ium) with spinneret. though the correspondence has been doubted by some students. The body of the caterpillar is usually cylindrical and wormlike, with the 5 After Packard, Mem. Nat. Acad. Sci. vol. vii.
FIG. 6. - Wing neuration of a Swift Moth (Hepialid). j, Jugum. Nervures numbered as in fig. 5. Note that there are five branches to the radial nervure (No. 3) in both foreand hindwing, and that the median trunk nervures (No. 4) traverse the discoidal areolet.
B FIG. 7. - A, Arrangement of scales in rows on wing of Butterfly. n, Nervure; c, collar-like outgrowths of cuticle. Magnified. B, single scale, and C, an androconium more highly magnified.
segmentation well marked and the cuticle feebly chitinized and flexible. Firm chitinous plates are, however, not seldom present on the prothorax and on the hindmost abdominal segment. The segments are mostly provided with bristle or spine-bearing tubercles, whose arrangement has lately been shown by H. G. Dyar to give partially trustworthy indications of relationship. On either side of the median line we find two dorsal or trapezoidal tubercles (Nos. I and 2), while around the spiracle are grouped (Nos. 3, 4 and 5) supra-, post-, and pre-spiracular tubercles; below are the subspiraculars, of which there may be two (Nos. 6, 7). The last-named is situated on the base of the abdominal proleg, and yet another tubercle (No. 8) may be present on the inner aspect of the proleg. The spiracles are very conspicuous on the body of a caterpillar, occurring on the prothorax and on the first eight abdominal segments. Various tubercles may become coalesced or aborted (fig. Io, B); often, in conjunction with the spines that they bear, the tubercles serve as a valuable protective armature for the caterpillar. Much discussion has taken place as to whether the abdominal prolegs are or are not developed directly from the embryonic abdominal appendages. In the more lowly families of Lepidoptera, these organs are provided at the extremity with a complete circle of hooklets, but in the more highly organized families, only the inner half of this circle is retained.
The typical Lepidopteran pupa, or " chrysalis," as shown in the higher families, is an obtect pupa (fig. I I) with no trace of mandibles, the appendages being glued to the body by an exudation, and B, after Grote, Mitt. alts dem Roemer Museum, No. 6.
FIG. Io. - Abdominal segments of Caterpillars, to show arrangement of tubercles; the arrows point anteriorly. A, Generalized condition; B, specialized condition in the Saturniidae. s, Spiracle; the numbering of the tubercles is explained in the text. Note that in FIG. II. - PUpa B No. 2 is much reduced and disappears of a Butterfly after the first moult. 4 and 5 are (Amathusia phi- coalesced, and 6 is absent. dippus). motion being possible only at three of the abdominal intersegmental regions, the fifth and sixth abdominal segments at most being " free." A flattened or pointed process - the cremaster - often prominent at the tail-end, may carry one or several hooks (fig. I, d) which serve to anchor the pupa to its cocoon or to suspend butterfly-pupae from their pad of silk (fig. II). In the lower families the pupa (fig. I, c) is only incompletely obtect, and a greater number of abdominal segments can move on one another. The seventh abdominal segment is, in all female lepidopterous pupae, fused with those behind it; in the male " incomplete " pupa this becomes " free " and so may the segments anterior to it, in both sexes, forward to and including the third. The presence of circles of spines on the abdominal segments enables the " incomplete " pupa as a whole to work its way partly out of the cocoon when the time for the emergence of the imago draws near. In the family of the Eriocraniidae (often called the Micropterygidae) the pupa resembles that of a caddis-fly (Trichopteron) being active before the emergence of the imago and provided with strong mandibles by means of which it bites its way out of the cocoon. The importance of the pupa in the phylogeny and classification of the Lepidoptera has lately been demonstrated by T. A. Chapman in a valuable series of papers. Sometimes organs are present in the pupa which are undeveloped in the imago, such as the maxillary palps of the Sesiidae (clearwing moths) and the pectination on the feelers of female Saturniids. E. B. Poulton has drawn attention to the ancestral value of such characters.
Habits and Life-Relations
The attractiveness of the Lepidoptera and the conspicuous appearance of many of them have led to numerous observations on their habits. The method of feeding of the imago by the suction of liquids has already been mentioned in connexion with the structure of the maxillae and the foodcanal. Nectar from flowers is the usual food of moths and butterflies, most of which alight on a blossom before thrusting the proboscis into the corolla of the flower, while others - the hawk moths (Sphingidae) for example - remain poised in the air in front of the flower by means of excessively rapid vibration of the wings, and quickly unrolling the proboscis sip the nectar. Certain flowers with remarkably long tubular corollas seem to be specially adapted for the visits of hawk moths. Some Lepidoptera have other sources of food-supply. The juices of fruit are often sought for, and certain moths can pierce the envelope of a succulent fruit with the rough cuticular outgrowths at the tips of the maxillae, so as to reach the soft tissue within. Animal juices attract other Lepidoptera, which have been observed to suck blood from a wounded mammal; while putrid meat is a familiar " lure " for the gorgeous " purple emperor " butterfly (Apatura iris). The water:of streams or the dew on leaves may be frequently sought by Lepidoptera desirous of quenching their thirst, possibly with fatal results, the insects being sometimes drowned in rivers in large numbers. Members of several families of the Lepidoptera - the Hepialidae, Lasiocampidae and Saturniidae, for example - have the maxillae vestigial or aborted, and take no food at all after attaining the winged condition. In such insects there is a complete " division of labour " between the larval and the imaginal instars, the former being entirely devoted to nutritive, the latter to reproductive functions.
Of much interest is the variety displayed among the Lepidoptera in the season and the duration of the various instars. The brightly coloured vanessid butterflies, for example, emerge from the pupa in the late summer and live through the winter in sheltered situations, reappearing to lay their eggs in the succeeding spring. Many species, such as the vapourer moths (Orgyia), lay eggs in the autumn, which remain unhatched through the winter. The eggs of the well-known magpie moths (Abraxas) hatch in autumn and the caterpillar hibernates while still quite small, awaiting for its growth the abundant food-supply to be afforded by the next year's foliage. The codlin moths (Carpocapsa) pass the winter as resting full-grown larvae, which seek shelter and spin cocoons in autumn, but do not pupate until the succeeding spring. Lastly, many of the Lepidoptera hibernate in the pupal stage; the death's head moth (Acheronitia) and the cabbage-white butterflies (Pieris) are familiar examples of such. The last-named insects afford instances of the " double-brooded " condition, two complete life-cycles being passed through in the year. The flour moth (Ephestia kiihniella) is said to have five successive generations in a twelvemonth. On the other hand, certain species whose larvae feed in wood or on roots take two or three years to reach the adult stage.
The rate of growth of the larva depends to a great extent on the nature of its food, and the feeding-habits of caterpillars afford much of interest and variety to the student. The contrast among the Lepidoptera between the suctorial mouth of the imago and the biting jaws of the caterpillar is very striking (cf. figs. 4 and 9), and the profound transformation in structure which takes place is necessarily accompanied by the change from solid to liquid food. The first meal of a young caterpillar is well known to be often its empty egg-shell; from this it turns to feed upon the leaves whereon its provident parent has laid her eggs. But in a few cases hatching takes place in winter or early spring, and the young larvae have then to find a temporary food until their own special plant is available. For example, the caterpillars of some species of Xanthia and other noctuid moths feed at first upon willow-catkins. On the other hand, the caterpillars of the pith moth (Blastodacna) hatched at midsummer, feed on leaves when young, and burrow into woody shoots in autumn. All who have tried to rear caterpillars know that, while those of some species will feed only on one particular species of plant, others will eat several species of the same genus or family, while others again are still less particular, some being able to feed on almost any green herb. It is curious to note how certain species change their food in different localities, a caterpillar confined to one plant in some localities being less particular elsewhere. Individual aberrations in food are of special interest in suggesting the starting-point for a change in the race. When we consider the vast numbers of the Lepidoptera and the structural modifications which they have undergone, their generally faithful adherence to a vegetable diet is remarkable. The vast majority of caterpillars eat leaves, usually devouring them openly, and, if of large size, quickly reducing the amount of foliage on the plant. But many small caterpillars keep, apparently for the sake of concealment, to the under surface of the leaf, while others burrow into the green tissue, forming a characteristic sinuous " mine " between the two leaf-skins. In several families we find the habit of burrowing in woody stems, - the " goat " (Cossus, fig. 8) and the clearwings (Sesiidae), for example, while others, like the larvae of the swift moths (Hepialidae) live underground devouring roots (fig 12). The richer nutrition in the green food is usually shown by the quicker growth of the numerous caterpillars that feed on it, as compared with the slower development of the wood and root-feeding species. Aquatic larvae are very rare among the Lepidoptera. The caterpillars of the pyralid " china-mark " moths (Hydrocampa), (fig. 13), however, live under water, feeding on duckweed (Lemna) and breathing atmospheric air, a film of which is enclosed in a spun-up shelter beneath the leaves, while the larvae of Paraponyx, which feed on Stratiotes, have closed spiracles and breathe dissolved air by means of branchial filaments along the sides of the body.
FIG. 12. - Larva of Hepialus humuli (ghost moth).
We may now turn to instances of more anomalous modes of feeding. The clothes moths (Tineids) have invaded our dwellings and found a congenial food-stuff for their larvae in our garments. A few small species of the same group are reared in meal and other human food-stores; so are the caterpillars of some pyralid moths (Ephestia), while others (Asopia, Aglossa) feed upon kitchen refuse. Two species of crambid moths (Aphomia sociella and Galleria melonella) find a home in bee-hives, where their caterpillars feed upon the wax, while the waxy secretion from the body of the great American lantern-fly (Fulgora candelaria) serves both as shelter and food for the caterpillar of the moth Epipyrops anomala. Very few caterpillars have developed a thoroughly carnivorous habit. That of Cosmia trapezina feeds on oak and other leaves, but devours smaller caterpillars which happen to get in its way, and if shaken from the tree, eats other larvae while climbing the trunk. Xylina ornithopus and a few other species are said to be always carnivorous when opportunity offers; the small looping caterpillar of a " pug " moth (Eupithecia coronata) has been observed to eat a larva three times as big as itself. The caterpillars of Orthosia pistacina live together in peace while their food is moist, but devour each other when it dries up; this is true cannibalism - a term which should not be applied to the habit of preying on another species. A few carnivorous caterpillars do not attack other caterpillars, but prey upon insects of another order; among these Fenescia tarquinius, which eats aphides, and Erastria scitula, which feeds upon scale insects, must be reckoned as benefactors to mankind. The life-history of the latter moth has been worked out by H. Rouzaud. It inhabits the shores of the Mediterranean, and its caterpillar devours the coccids upon various fruit-trees, especially the black-scale (Lecanium oleae) of the olive. The moth, which is a small noctuid, the white markings on whose wings give it the appearance of a bird-dropping when at rest in the daytime, appears in May, and lays her eggs, singly and far apart, upon the trees infested by the coccids. When hatched, the young caterpillar selects a large female coccid, eats its way through the scale, and devours the insect beneath; having done this it makes its way to a fresh victim. As it increases in size it forms a case for itself made of the scales of its victims, excrement, &c., bound together by silk which it spins, and, protected by this covering, which closely resembles the smut-covered bark of the tree, it roams about during its later stages, devouring several coccids every day. So nutritious is the food, that four or five successive broods follow each other through the summer.
The habit just mentioned of forming some kind of protective covering out of foreign substances spun together by silk is practised by caterpillars of different families. The clothes moth larvae (Tinea, fig. 54), for example, make a tubular dwelling out After Marlatt (after Riley), Bull. 4, Div. Ent. U.S. Dept. Agr. FIG. 14. - Clothes Moth (Tinea pellionella), with larva in and out of_its case. Magnified.
of the pellets of wool passed from their own intestines, while the allied Tortricid caterpillars roll up leaves and spin for themselves cylindrical shelters. The habit of spinning over the food plant a protective mass of web, whereon the caterpillars of a family can live together socially is not uncommon. In the case of the small ermine moths (Hyponomeuta) the caterpillars remain associated throughout their lives and pupate in cocoons on the mass of web produced by their common labour. But the larger, spiny caterpillars of the vanessid butterflies usually scatter away from the nest of their infancy when they have attained a certain size.
Spines and hairs seem to be often effective protections for caterpillars; the experiments of E. B. Poulton and others tend to show that hairy caterpillars (fig. 15) are distasteful to birds. Many caterpillars are protected by the harmony of their general green coloration with their surroundings. When the insect attains a large size - as in the case of the hawk moth (Sphingid) caterpillars - the extensive green surface becomes broken up by diagonal dark markings (fig. 46b), thus simulating the effect of light and shade among the foliage. A remarkable result of Poulton's experiments has been the establishment of a reflex effect through the skin on the colour of a caterpillar. Some species of " loopers " (Geometridae, fig. 43) for example, if placed when young among surroundings of a certain colour, become closely assimilated thereto - dark brown among dark twigs, green among green leaves. These colour-reflexes in conjunction with the elongate twig-like shape of the caterpillars and their habit of stretching themselves straight out from a branch, afford some of the best and most familiar examples of " protective resemblance." The " terrifying attitude " of caterpillars, and the supposed resemblance borne by some of them to serpents and other formidable vertebrates or arthropods, are discussed in the article Mimicry.
The silk produced by a caterpillar is, as we have seen, often advantageous in its own life-relations, but its great use is in connexion with the pupal stage. In the life-history of many Lepidoptera, the last act of the caterpillar is to spin a cocoon which may afford protection to the pupa. In some cases this is formed entirely of the silk produced by the spinning-glands, and may vary from the loose meshwork that clothes the pupa of the FIG. 13. - Hydrocampa aquatilis (water moth).
FIG. 15. - Larva of Orgyia gonostigma. Europe.
diamond-back moth (Plutella cruciferarum) to the densely woven cocoon of the silkworms (Bombycidae and Saturniidae) or the hard shell-like covering of the eggars (Lasiocampidae). Frequently foreign substances are worked up with the silk and serve to strengthen the cocoon, such as hairs from the body of the caterpillar itself, as among the " tigers " (Arctiidae) or chips of wood, as with the timber-burrowing larva of the " goat " (Cossus) . In many families of Lepidoptera we can trace a degeneration of the cocoon. Thus, the pupae of most owl moths (Noctuidae) and hawk moths (Sphingidae) lie buried in an earthen cell. Among the butterflies we find that the cocoon is reduced to a pad of silk which gives attachment to the cremaster; in the Pieridae there is in addition a girdle of silk around the waist-region of the pupa, but the pupae of the Nymphalidae (figs. II, 65) simply hang from the supporting pad by the tail-end. Poulton has shown that the colours of some exposed pupae vary with the nature of the surroundings of the larva during the final stage.
When the pupal stage is complete the insect has to make its way out of the cocoon. In the lower families of moths it is the pupa which comes out at least partially, working itself onwards by the spines on its abdominal segments; the pupa of the primitive Micropteryx has functional mandibles with which it bites through the cocoon. In the higher Lepidoptera the pupa is immovable, and the imago, after the ecdysis of the pupal cuticle, must emerge. This emergence is in some cases facilitated by the secretion of an acid or alkaline solvent discharged from the mouth or from the hind-gut, which weakens the cocoon - so that the delicate moth can break through without injury.
As might be expected, the conditions to which larva and pupa are subjected have often a marked influence on the nature of the imago. An indifferent food-supply for the larva leads to a dwarfing of the moth or butterfly. Many converging lines of experiment and observation tend to show that cool conditions during the pupal stage frequently induce darkening of pigment in the imago, while a warm temperature brightens the colours of the perfect insect. For example, in many species of butterfly that are double-brooded, the spring brood emerging from the wintering pupae are more darkly coloured than the summer brood, but if the pupae producing the latter be subjected artificially to cold conditions, the winter form of imago results. It is usually impossible, however, to produce the summer form of the species from wintering pupae by artificial heat. From this A. Weismann argued that the more stable winter form must be regarded as representing the ancestral race of the species. Further examples of this " seasonal dimorphism " are afforded by many tropical butterflies which possess a darker " wet-season " and a brighter " dry-season " generation. So different in appearance are often these two seasonal forms that before their true relationship was worked out they had been naturally regarded as independent species. The darkening of wingpatterns in many species of Lepidoptera has been carefully studied in our own British fauna. Melanic or melanochroic varieties are specially characteristic of western and hilly regions, and some remarkable dark races (fig. 43) of certain geometrid moths have arisen and become perpetuated in the manufacturing districts of the north of England. The production of these melanic forms is explained by J. W. Tutt and others as largely due to the action of natural selection, the damp and sooty conditions of the districts where they occur rendering unusually dark the surfaces - such as rocks, tree-trunks and palings - on which moths habitually rest and so favouring the survival of dark, and the elimination of pale varieties, as the latter would be conspicuous to their enemies. Breeding experiments have shown that these melanic races are sometimes " dominant " to their parent-stock. An evidently adaptive connexion can be frequently traced between the resting situation and attitude of the insect and the colour and pattern of its wings. Moths that rest with the hindwings concealed beneath the forewings (fig. 34, f) often have the latter dull and mottled, while the former are sometimes highly coloured. Butterflies whose normal resting attitude is with the wings closed vertically over the back (fig. 63) so that the under surface is exposed to view, often have this under surface mottled and inconspicuous although the upper surface may be bright with flashing colours. Various degrees of such " protective resemblance " can be traced, culminating in the wonderful " imitation " of its surroundings shown by the tropical " leaf-butterflies " (Kallima), the under surfaces of whose wings, though varying greatly, yet form in every case a perfect representation of a leaf in some stage or other of decay, the butterfly at the same time disposing of the rest of its body so as to bear out the deception. How this is effected is best told by A. R. Wallace, who was the first to observe it, in his work The Malay Archipelago: " The habit of the species is always to rest on a twig and among dead or dried leaves, and in this position, with the wings closely pressed together, their outline is exactly that of a moderately sized leaf slightly curved or shrivelled. The tail of the hindwings forms a perfect stalk and touches the stick, while the insect is supported by the middle pair of legs, which are not noticed among the twigs and fibres that surround it. The head and antennae are drawn back between the wings so as to be quite concealed, and there is a little notch hollowed out at the very base of the wings, which allows the head to be retracted sufficiently." But the British Vanessids often rest on a bare patch of ground with the brightly coloured upper surface of their wings fully exposed to view, and even make themselves still more conspicuous by fanning their wings up and down. Some genera and families of Lepidoptera, believed to secrete noxious juices that render them distasteful, are adorned with the staring contrasts of colour usually regarded as " warning," while other genera, belonging to harmless families sought for as food by birds and lizards, are believed to obtain complete or partial immunity by their likeness to the conspicuous noxious groups. (See Mimicry.) Sexual dimorphism is frequent among the Lepidoptera. In many families this takes the form of more elaborate feelers in the male than in the female moth. Such complex feelers (fig. 2) bear numerous sensory (olfactory) nerve-endings and give to the males that possess them a wonderful power of discovering their mates. A single captive female of the Endromidae or Lasiocampidae often causes hundreds of males of her species to " assemble " around her prison, and this character is made use of by collectors who want to secure specimens. In many butterflies - notably the " blues " (Lycaenidae) - the male is brilliant while the female is dull, and in other groups (the Danainae for example) he is provided with scent-producing glands believed to be " alluring " in function. The apparent evidence given by the sexual differences among the Lepidoptera in favour of C. Darwin's theory of sexual selection finds no support from a study of their habits. The male indeed usually seeks the female, but she appears to exercise no choice in pairing. In some cases the female is attracted by the male, and here a modified form of sexual selection appears to be operative. The ghost swift moth (Hepialus humuli) affords a curious and interesting example of this condition, the female showing the usual brown and buff coloration of her genus, while the wings of the male are pure white, rendering him conspicuous in the dusky evening when pairing takes place. But in the northernmost After Ratzeburg, Insect Life, vol. 2 (U.S. Dept. Agr.).
FIG. 16. - Pupa of Gypsy Moth (Porthetria dis par) sheltered in leaves joined by silken threads. Below is the cast larval cuticle.
A B FIG. 17. - Vapourer Moth (Ocneria detrita). S. Europe. A, Male; B,'Female.
haunts of the species, where there is no midsummer night, the male closely resembles the female in wing patterns, the development of the conspicuous white being needless. A very interesting sexual dimorphism is seen in the wingless condition of several female moths - the winter moths (Hybernia and Cheimatobia) among the Geometridae and the vapourers (Orgyia and Ocneria) among the Lymantriidae for example (fig. 17). It might be thought that the loss of power of flight by the female would seriously restrict the range of the species. In such insects, however, the caterpillars are often active and travel far.
Classification
The order Lepidoptera contains more than fifty families, the discussion of whose mutual relationships has given rise to much difference of opinion. The generally received distinction is between butterflies or Rhopalocera (Lepidoptera with clubbed feelers, whose habit is to fly by day) and moths or Heterocera (Lepidoptera with variously shaped feelers, mostly crepuscular or nocturnal in habit). This distinction is quite untenable as a zoological conception, for the relationship of butterflies to some moths is closer than that of many families of Heterocera to each other. Still more objectionable is the division of the order into Macrolepidoptera (including the butterflies and large moths) and the Microlepidoptera (comprising the smaller moths). Most of the recent suggestions for the division of the Lepidoptera into sub-orders depend upon some single character. Thus J. H. Comstock has proposed to separate the three lowest families, which have - like caddis-flies (Trichoptera) - a jugum on each forewing, as a sub-order Jugatae, distinct from all the rest of the Lepidoptera - the Frenatae, mostly possessing a frenulum on the hindwing. A. S. Packard places one family (Micropterygidae) with functional mandibles and a lacinia in the first maxilla alone in a sub-order Laciniata, all the rest of the order forming the sub-order Haustellata. T. A. Chapman divides the families with free or incompletely obtect and mobile pupae (Incompletae) from those with obtect pupae which never leave the cocoon (Obtectae), and this is probably the most natural primary division of the Lepidoptera that has as yet been suggested. Dyar puts forward a classification founded entirely on the structure of the larva, while Tutt divides the Lepidoptera into three great stirps characterized by the shape of the chorion of the egg. The primitive form of the egg is oval, globular, or flattened with the micropyle at one end; from this has apparently been derived the upright form of egg with the micropyle on top which characterizes the butterflies and the higher moths. These schemes, though helpful in pointing out important differences, are unnatural in that they lay stress on single, often adaptive, characters to the exclusion of others equally important. Although it is perhaps best to establish no division among the Lepidoptera between the order and the family, an attempt has been made in the classification adopted in this article to group the families into tribes or super-families which may indicate their probable affinities. The systematic work of G. F. Hampson, A. R. Grote and E. Meyrick has done much to place the classification of the Lepidoptera on a sound basis, so far as the characters of the imago are concerned, but attention must also be paid to the preparatory stages if a truly natural system is to be reached.
Jugatae. Three families are included in this group having in common certain primitive characters of the wings and neuration (see fig. 6), as well as of the larva and pupa. There is a membranous lobe or j ugum near the base of the wing, and the neuration of the hindwing is closely like that of the forewing, the radial nervure being fivebranched in both. The pupa has four or five movable segments, and the larval prolegs have complete circles of hooklets.
The three families of the Jugatae are not very closely related to each other. The Micropterygidae (often known as Eriocephalidae), comprising a few small moths with metallic wings, are the most primitive of all Lepidoptera. They are provided with functional mandibles, while the maxillae have distinct laciniae, well-developed palps and galeae not modified for suction (see fig. 3). The larva is remarkable on account of its long feelers, the presence of pairs of jointed prolegs on the first eight abdominal segments, an anal sucker beneath the last segment and bladder-like outgrowths on the cuticle. These curious larvae feed on wet moss. The family has only a few genera scattered widely over the earth's surface (Europe, America, Australia, New Zealand).
The Eriocraniidae resemble the Micropterygidae in appearance, but the imago has no mandibles, and the maxillae, though short and provided with conspicuous palps, have no laciniae and form a proboscis as in Lepidoptera generally. The abdomen of the female carries a serrate piercing process, and the eggs are laid in the leaves of deciduous trees, the white larvae, with aborted legs, mining in the leaf tissue. The fully-fed larva winters in an underground cocoon and then changes into the most remarkable of all known lepidopterous pupae, with relatively enormous toothed mandibles which bite a way out of the cocoon in preparation for the final change. These pupal mandibles of the Eriocraniidae, together with the nature of the imaginal maxillae in the Micropterygidae (Eriocephalidae) and the wing-neuration in both families, point strongly to a relationship between the Lepidoptera and the Trichoptera.
The Hepialidae or swift moths - the third family of the Jugataeare in some respects specialized. The moths are of large or moderate size with the maxillae in a vestigial condition, no food being taken after the attainment of the perfect state. The larvae (fig. 12) feed either on roots or in the wood of trees and shrubs, not attaining their growth in less than a year and some large exotic species living for two or three. The family is world-wide in range, and Australia possesses some almost gigantic and strangely coloured genera.
Tineides. A large assemblage of moths, mostly of small size, are included in this group. The wings have no jugum, but there is a frenulum on the hindwing, which has, as in all the groups above the Jugatae, only a single radial nervure. Three anal nervures are present in the hindwing in those families whose wings are well developed, but in several families of small moths the wings of both pairs are very narrow and pointed, and the neuration is consequently reduced. The sub-costal nervure of the hindwing is usually present and distinct from the radial nervure. The egg is flat except in the Cossidae and Castniidae in which it is upright. The larval prolegs, with few exceptions, have a complete circle of hooklets, and the larvae usually feed in some concealed situation. The pupa is incompletely obtect, with three (in some females only two) to five free abdominal segments, and emerges partly from the cocoon before the moth appears. The cremaster serves to anchor the pupa to its cocoon at the correct degree of emergence, and thus facilitates the eclosion of the imago.
The Cossidae are a small family of large moths (figs. 8, 18, 19) belonging to this section, characterized by their heads with erect rough scales or hairs, the pectinate feelers of the males, their reduced maxillae so that no food is taken in the perfect state, and their wings with the fifth radial nervure arising from the third, and the main median nervure forking in the discoidal areolet. The larvae feed in plant stems, often in the wood of trees, forming tunnels and galleries, and usually taking a year or more to reach maturity. The pupa which has three or four free segments in the male and four or five in the female, rests in a cocoon within the food plant, often strengthened by chips of wood, or in a subterranean cocoon. The family is fairly well represented in the tropics; the British fauna possesses only three species, of which the " goat " (Cossus cossus) and the " leopard " (Zeuzera pyrina) are well known, the caterpillars of both being often injurious to timber and fruit trees.
The Tortricidae are a large family of small moths (see fig. I), nearly allied to the Cossidae. The fifth radial nervure does not arise from the third, the maxillae are well developed, but their palps are obsolete; the head is densely clothed with erect scales; the terminal segment of the labial palp is short and obtuse. The female pupa has three, the male four, free segments. All the larvae of these moths have some method of concealing themselves while feeding. A frequent plan is to roll up a leaf of the food-plant, fastening the twisted portion with silken threads so as to make a tubular retreat; this is the habit of the caterpillar of the green bell moth (Tortrix viridana) which often ravages the foliage of oak plantations. The larvae of the pine-shoot moths (Retinia) shelter in solidified resinous exudations from their coniferous food-plants, while the codlin-moth caterpillar (Carpocapsa pomonella) feeds in apples and pears, growing with the growth of the fruit which affords them both provender and home. The antics of " jumping-beans " are due to the movements of tortricid caterpillars within the substance of the seed.
The Psychidae are a small but widely-distributed family of moths whose males have the head, densely clothed with rough hairs, bearing complex, bipectinated feelers, but with the maxillae reduced and useless. The larvae live in portable cases made of grass, pieces of leaf or stick, with a silken lining, and these cases serve as-cocoons for the pupae which agree in structure with those of the Tortricidae. But the most remarkable feature of the family is the extreme degradation of the female, which, wingless, legless and without jaws or feelers, never emerges from the cocoon.
The Castniidae are a small family of large, conspicuous, day-flying exotic moths (fig.
20) whose clubbed feelers and bright colours give them a resemblance to butterflies, although their wingneuration is of the primitive t in e o i d type; the smooth larvae feed on the stems or roots of plants and the pupal structure agrees with that of the Tortricidae and FIG. 20. - Castnia acraeoides. Brazil. Psychidae. The distribution of the family is confined to Tropical America and the Indo-Malayan and Australian regions.
The Zygaenidae (burnet moths) are a large family of day-flying moths (fig. 21) adorned with brilliant metallic colours. The feelers are long, stout in the middle and tapering, bearing numerous long or short pectinations. The well-developed maxillae have vestigial palps. The larvae - often very conspicuously coloured - are remarkable among the Tineides in having incomplete circles of hooks on the prolegs, and they feed exposed on the leaves of various plants. The pupa, enclosed in a silken cocoon, has four or five free segments. The Limacodidae are a small FIG. 2 I: Neuro- family of brownish nocturnal moths, allied to symploca concinna. the Zygaenidae and agreeing with them in the S. Africa. structure of the pupa. The larva in this family also is an exposed feeder, but it is remarkable in form, being flattened and slug-like, without prolegs and adorned with curious spinous processes.
The Sesiidae are a large family of small, narrow-winged moths, the sub-costal nervure of the hindwing being absent and the wings being for the most part destitute of scales (fig. 22). The maxillae are developed but their palps are vestigial, while the terminal segment of the labial palp is short and pointed. Many of these insects have their bodies banded with black and yellow; this in conjunction with the transparent wings makes some of them like wasps or hornets in appearance. The larvae feed in the woody stems of various A B plants. The pupa, with FIG. 22. - A, Sesia asiliformis (Gad-fly three or four free abHawk Moth). Europe. B, Larva. dominal segments, re mains within its cocoon, formed with chips of wood, until the time for its final change draws near; then it works itself partly out of the tree by means of the spines on its abdominal segments.
The Nepticulidae are the smallest of all the Lepidoptera, measuring only 3-8 mm. across the outspread wings, which are all lanceolate and pointed at the tip. The sucking portions of the maxillae are vestigial, but the palps are long and jointed. The larvae, without FIG. 1 8. - Stygia australis. S. Europe.
FIG. 19. - Zeuzera scalaris. India.
?----???, ? ...- /";% ?? A, 4@ 494 thoracic limbs or prolegs, but sometimes with paired rudimentary processes on some of the segments, mine in the leaves of plants. The pupa, with four free abdominal segments in the female and five in the male, rests in a cocoon usually outside the mine.
The Adelidae are a family of delicate, but larger, moths with very long feelers (fig. 23) especially in the males. The larvae feed, when young, in flowers, later, protected by a flat case, they devour leaves, the pupa resembles that of the Nepticulidae in structure. The female has an ovipositor adapted for piercing plant tissues.
The Tineidae are a large and important family of small moths (figs. 14, 24, 25) with rough-haired heads, and with the maxillae FIG. 23. - Adela FIG. 24. - Euplocampus FIG. 25. - Tinea degeerella. Europe. anthracinus. Europe. tapetzella (Clothes Moth). Europe.
and their palps usually well developed. Many of the genera have narrow pointed wings with degraded neuration. The larvae differ in their habits, some - Gracilaria for example - mine in leaves, while others, like the well-known caterpillars of the clothes moth (Tinea) surround themselves with portable cases (fig. 14) formed by spinning together their own excrement. The female pupa has three, the male four free abdominal segments.
Plutellides. This group includes a few large families of small moths that are linked by their imaginal and larval structure to the Tineidae (in which they have often been included) and by their pupal structure to the higher groups that have yet to be considered. The moths have labial palps with slender pointed terminal segments, and narrow pointed wings, but the neuration (except in the Elachistidae) is less degenerate than in most Tineidae. The hairy covering of the head is smooth, and the maxillary palps are usually vestigial. The egg is flat, and the larval prolegs have complete circles of hooklets. The pupa is obtect with only two free abdominal segments (fifth and sixth) in both sexes and does not move out of the cocoon.
Four families are included in this group. The Plutellidee (fig. 26) have the maxillary palps developed, in some genera, as slender threadlike appendages directed straight forward. The larvae do not usually mine in leaves, but feed openly, keeping to the underside for protection (Plutella), or spinning by their united labour a mass of web over the foodplant (Hyponomeuta). In the other three families the maxillary palps are vestigial or obsolete. The Elachistidae have remarkably narrow, pointed wings and their larvae mine in leaves or form portable cases and feed among seeds. In the Oecophoridae (fig. 27) the sub-costal nervure of the hindwing is free and distinct throughout its length, and the larvae usually feed among spun leaves or seeds, or in decayed wood. The Gelechiidae are a large family with similar larval habits; the moths are distinguished by the sinuate termen of the hindwing and the connexion of its sub-costal nervure with the discoidal areolet.
Pyralides. This group includes a number of moths of delicate build with elongate legs, the maxillae and their palps being usually well developed. The forewings have two anal nervures, the hindwings three (fig. 30, h, i); in the hindwing the subcostal nervure bends towards and often connects with the FIG. 28. - Ptero- FIG. 29. - Orneodes radial, and the phorus spilodactylus. hexadactylus (24-plumed f r e n u 1 u m i s Europe. Moth). Europe. usually present.
The egg is flat.
The larva has complete circles of hooklets on its five pairs of prolegs, and the pupa (usually completely obtect) does not move at all from its cocoon. This group includes the only Lepidoptera that have aquatic larvae.
Of the families comprised in this division three deserve special mention. The Pterophoridae (plume moths, fig. 28) usually have the wings deeply cleft - a single cleft in the forewing and two in the hindwing. The hairy larvae feed openly on leaves, while the soft and hairy pupa remains attached to its cocoon by the cremaster, although it is incompletely obtect and has three or four free abdominal segments. The Orneodidae (multiplume moths) have all the wings six-cleft. Our British species, Orneodes hexadactyla (fig. 29), is an exquisite little insect, whose larva feeds on the blossoms of honeysuckle. The pupa is completely obtect, with only two free abdominal segments. The Pyralidae (figs. 13, 30), a large family with numerous divisions, have entire wings, and their pupae are After Riley and Howard, Insect Life, vol. 2 (U.S. Dept. Agr.).
FIG. 30. - Flour Moth (Ephestia kiihniella). c, With wings spread. d, Head and front body-seg f At rest. [wings. ments of larva. g, h, i, Marking and neuration of e, 2nd and 3rd abdominal seg a, Larva. ments, more highly magni b, Pupa; twice natural size. fled.
obtect. The caterpillars feed in some kind of shelter, some spinning a loose case among the leaves of their food-plant, others burrowing into dry vegetable substances or eating the waxen cells of bees. Several species of this group, such as the Mediterranean flour moth, Ephestia kiihniella (fig. 30), become serious pests in storehouses and granaries, their larvae devouring flour and similar food-stuffs.
Noctuides. In this group may be included a number of families of moths with the second median nervure of the forewing arising close to the third. This feature of neuration characterizes also the Jugatae (see fig. 6), Tineides, Plutellides and Pyralides. But the Noctuides differ from these groups in having only two anal nervures in the hindwing. The maxillary palps are absent or vestigial, and a frenulum is usually present on the hindwing. The larva has usually ten prolegs, whose hooklets are arranged only along the inner edge, while the immobile pupa is always obtect with only two free abdominal segments (the fifth and sixth). The Lasiocampidae and their allies have flat eggs, but in the Noctuidae, Arctiidae and their allies the egg is upright.
The Lasiocampidae, together with a few small families, differ from the majority of this group in wanting a frenulum. The maxillae of the Lasiocampidae are so reduced that no food is taken in the imaginal state, and in correlation with this condition the feelers of the male are strongly (those of the female more feebly) bipectinated. The moths are stout, hairy insects, usually brown or yellow in the pattern of their wings. The caterpillars are densely hairy and many species hibernate in the larval stage. The pupa is enclosed in a hard, dense cocoon, whence the name " eggars " is often applied to the family, which has a wide distribution, but is absent from New Zealand. The Drepanulidae are an allied family, in which the frenulum is usually present, while the hindmost pair of larval prolegs are absent, their segment being prolonged into a pointed process which is raised up when the caterpillar is at rest. The hook-tip moths represent this family in the British fauna.
The Lymantriidae resemble the Lasiocampidae in their hairy bodies and vestigial maxillae, but the frenulum is usually present on the hindwing and the feelers are bipectinate only in the males. Some females of this family - the vapourer moths (Orgyia and allies, fig. 17), for example - are degenerate creatures with vestigial wings. The larvae (fig. 15) are very hairy, and often carry dense tufts on some of their segments; hence the name of " tussocks " frequently applied to them. The pupae are also often hairy (fig. 16) - an FIG. 31. - Claterna cydonia. India.
exceptional condition - and are protected by a cocoon of silk mixed with some of the larval hairs, while the female sheds some hairs from her own abdomen to cover the eggs. The family is widely distributed, its headquarters being the eastern tropics. To that part of the world is restricted the allied family of the Hypsidae, FIG. 32. - Ophideres imperator. Madagascar.
distinguished from the " tussocks " by the slender upturned terminal segment of the labial palps and by the development of the maxillae. The Noctuidae are the largest and most dominant family of the Lepidoptera, comprising some Io,000 known species. They are mostly moths of dull coloration, flying at dusk or by night. The maxillae are well developed, the hindwing has a frenulum, and its sub - costal nervure touches the radial near the base. The larvae of the Noctuidae (fig. 34, c) are rarely hairy and the pupa (fig. 34, d) usually rests in an earthen cell, being often the wintering stage for the species; sometimes the pupa is enclosed in a loose cocoon of silk and leaves. In some Noctuidae (fig. 32) the hindwings are brightly coloured, but these are concealed beneath the dull, inconspicuous forewings when the insect rests (fig. 34, f). Nearly allied to the Noctuidae, but very different in appearance, are the gaily-coloured Agaristidae, a family of day-flying moths (figs. 35, 36), confined to the warmer regions of the globe and distinguished by From Mally, Bull. 24, Div. Ent. U.S. Dept. Agr. FIG. 34. - e, f, Heliothis armigera. Europe. c, Larva; d, pupa in cell. Natural size. a, b, Egg, highly magnified.
their thickened feelers, those of the Noctuids being thread-like or slightly pectinate.
The Arctiidae (tiger moths, footmen, &c.) are allied to the Noctuidae, but their wing-neuration is more specialized, the sub-costal nervure of the hindwing being confluent with the radial for the basal part of its course. These moths (fig. 37) have gaily coloured wings, and the caterpillars are often densely covered with long smooth hairs. The pupae are enclosed in silken cocoons (fig. 38). The highest specialization of structure in this group of the Lepidoptera is reached by the Syntomidae, a family nearly allied to the Arctiidae, but with the sub-costal nervure in the hindwing absent. The Syntomidae have elongate narrow forewings and short hindwings, usually dark in colour with clear spots and dashes destitute of FIG. 35. - Rothia pales. Madagascar.
scales (fig. 40). The body, on the other hand, is often brilliantly adorned. The family, abundant in the tropics of the Old World, has only two European species.
Sphingides. This group includes a series of families which agree with the Noctuides in most points, but are distinguished by the origin of the FIG. 36. - A egocera rectilinea. FIG. 37. - Haploa Lecontei. Tropical Africa. N. America.
second median nervure of the forewing close to the first, or from the discocellular nervure midway between the first and third medians (see fig. 5). These neurational characters may appear somewhat insignificant, but such slight though constant distinctions in structures of no adaptational value may be safely regarded as truly significant of relationship. Several of the families in this After Lugger, Riley and Howard, Insect Life, vol. a (U.S. Dept. Agr.).
FIG. 38. - c, Tiger Moth (Phragmatobia fuliginosa, Linn.). Europe. a, Caterpillar; b, cocoon with pupa. Slightly enlarged.
group have lost the frenulum. In larval and pupal characters the Sphingides generally resemble the Noctuides, but in some families there is a reduction in the number of the larval prolegs. The egg is spherical or flat, upright only in the Notodontidae.
The Notodontidae are stout, hairy moths (figs. 5, 41, 42 a) with maxillae and frenulum developed. In the larva the prolegs on the FIG. 39. - Halias prasinana. Europe. FIG. 40. - Euchromia formosa. S. Africa.
hindmost segment are sometimes modified into pointed outgrowths which are carried erect when the caterpillar moves about. From these structures whip-like, coloured processes are protruded by the caterpillar (fig. 42 b) of the puss moth (Cerura) when alarmed; these processes are believed to help in " terrifying " the caterpillar's enemies. Allied to the Notodontidae are the Cymatophoridae - a family of moths agreeing with the Noctuidae in appearance and habits - and the large and important family of the Geometridae. FIG. 33. - Cyligramma fluctuosa. W. Africa.
The moths (fig. 43) of this family are distinguished from the Notodontidae by their delicate build and elongate feet, the caterpillars (fig. 43, c) by the absence or vestigial condition of the three anterior pairs of prolegs. The two hinder pairs of prolegs are therefore alone FIG. 41. - Notodonta ziczac (Pebble Prominent Moth). Europe.
Gil FIG. 42b. - Larva of Cerura (Puss Moth).
functional and the larva progresses by " looping," i.e. bending the body so as to bring these prolegs close up to the thoracic legs, and then, taking a fresh grip on the twig whereon it walks, stretching the body straight out again. Many of these larvae have a striking After Grote, Natural Science (J. M. Dent & Co.).
FIG. 43. - Geometrid Moth (Amphidasys betularia, Linn.). Europe. a, Large grey type; b, dark variety; c, caterpillar in looping attitude.
resemblance both in form and colour to the twigs of their foodplant. In some of the species the female has the wings reduced to useless vestiges. The family is world-wide in its range. The tropical Uraniidae are large handsome moths (figs. 44, 45), often with ex FIG. 44. - Urania boisduvalii. Cuba.
quisite wing-patterns, allied to the Geometridae, but distinguished by the absence of a frenulum in the moth and the presence of the normal ten prolegs in the larva.
The Sphingidae (hawk moths) are insects often of large size (figs. 46a, 47), with spindle-shaped feelers, elongate and powerful forewings and the maxillae very well developed. The hindwing carries a frenulum and has its sub-costal nervure connected with the radial by a short bar. The caterpillars have the full number of prolegs, and, in many genera, carry a prominent dorsal horn on the eighth abdominal segment (fig. 46 b). The pupa lies in an earthen cell. On account of their powerful flight the moths of this family have a wide range; certain species - like Acheronlia atropos and Protoparce convolvuli - migrate numbers almost every summer.
FIG. 46a. - Chlaenogramma jasminearum (Jessamine Sphinx). N. America.
A group of families in which the first maxillae are vestigial, the feelers bipectinate and the pupa enclosed in a have been regarded as the most highly specialized of all the moths, though according to other views the whole series of the Lepidoptera culminates in the Syntomidae. Of these cocoonspinning families may be specially mentioned the Eupterotidae, large brown or yellow moths inhabiting tropical Asia and Africa, and represented in Europe only by the " processionary moth" (Cnethocampa processionea). In this family the frenulum is present, and the larvae are protected with tufts of long hair. The Bombycidae have no frenulum, and FIG. 47. - Smerinthus ocellatus (Eyed Hawk moth). Europe.
the larvae are smooth, with some of the segments humped and the eighth abdominal often carrying a dorsal spine. The family in Islands British into the dense silken cocoon, FIG. 42a. - Cerura borealis. N. America.
FIG. 45. - Urania boisduvalii at rest, showing under surface of wings.
its distribution, but the common silkworm (Bombyx has become acclimatized in southern Europe and is most of the silk used in manufacture and art. Of After C. V. Riley, Bull. rg, Div. Ent. U.S. Dept. Agr. FIG. 48. Bombyx mori. China. a, Caterpillar (the common silk-worm); b, cocoon; c, male moth.
commercial value also is the silk spun by the great moths of the family Saturniidae, well represented is warm countries and contributing a single species (Saturnia pavonia-minor) to the British fauna. These moths (fig. 49) have but a single anal nervure in the hindwing and only three radial nervures in the forewing. The wing-patterns are handsome and striking; usually an unsealed " eyespot " is conspicuous at the end of each discoidal areolet. The Grypocera. This group stands at the base of the series of families that are usually distinguished as " butterflies." The feelers are recurved at the tip, and thickened just before the extremity. The forewing has the full number of radial nervures, distinct and evenly spaced, and two anal nervures; the frenulum is usually absent. The larvae (fig. 51) have prolegs with complete circles of hooklets, and often feed in concealed situations, while the pupa is protected by a light cocoon. The affinities of this group are clearly not with the higher groups of moths just described, but with some of the lower families. According to Meyrick they are most closely related to the Pyralidae, but Hampson and most other students would derive them (through the Castniidae) from a primitive Tineoid stock allied to the Cossidae and Zygaenidae.
Three families are included in the section. The North American Megathymidae and the Australian Euschemonidae have a frenulum and are usually reckoned among the " moths." The Hesperiidae in which the frenulum is wanting form the large family of the skipper butterflies, represented in our own fauna by several species. They are insects with broad head - the feelers being widely separated - usually brown or grey wings (fig. 50) and a peculiar jerky flight. The family has an extensive range but is unknown in Greenland, New Zealand, and in many oceanic islands.
Rhopalocera. This group comprises the typical butterflies which are much more highly specialized than the Grypocera, and may be readily distinguished by the knobbed or clubbed feelers and by the absence of a frenulum. Two or more of the radial nervures in the forewing arise from a common stalk or are suppressed. The egg is " upright." The larvae have hooklets only on the inner edges of the prolegs. The pupa is very highly modified, only two free abdominal segments are ever recognizable, and in some genera even thesehave become consolidated. The cocoon is reduced to a pad of silk, to which the pupa is attached, suspended by the cremastral hooks; in some families there is also a silken girdle around the waist-region. In correlation with the exposed condition of the pupa, we find the presence of a specially developed FIG. 51. - Chrysalis and head-piece " or " nose-horn " to Larva of Ni s o n i a d e s t a g e s protect the head-region of the con- (dingy skipper). Europe. tamed imago. Their bright colours and conspicuous flight ,in the sunshine has made the Rhopalocera the most admired of all insects by the casual observer.
A modification that has taken place in several families of butterflies is the reduction of the first pair of legs. H. W. Bates arranged the families in a series depending on this character, but neurational and pupal features must be taken FIG.152. - Chrysophanus thoe. N. America.
into account as well, and - the sequence followed here is modified from that proposed by A. R. Grote and J. W. Tutt.
The Lycaenidae are a large family including the small butterflies (figs. 52, 53, 54) popularly known as blues, coppers and hairstreaks. The forelegs in the female are normal, but in the male the tarsal segments - are shortened and the claws sometimes are absent. The forewing has only three or four radial nervures (fig.55),the last two of which arise from a common stalk; the feelers are inserted close together on the head. The larva is short and hairy, somewhat like a woodlouse in shape, the broad sides concealing the legs and prolegs, while the pupa, which is also hairy or bristly, is attached by the cremaster to a silken pad and cinctured with a silken thread. The upper surfaces of the wings of these insects are usually of a bright metallic hue - blue _ or coppery - while beneath there are often FIG. 53. - Rathinda amor. India. FIG. 54. - Cheritra freja. India.
numerous dark centred " eye-spots." The family is widely distributed. Nearly related are the Lemoniidae, a family abundantly represented in the Neotropical Region, but scarce in the Old World and having only a single European species (Nemeobius lucinia) which occurs also in England. In the Lemoniidae (figs. 56, 57) the forelegs of the male are reduced and useless for walking. The Libytheidae may be recognized by the elongate snout-like palps, is tropical in mori, fig. 48) the source of FIG. 49. - Epiphora bouhiniae. W. Africa.
caterpillars are protected by remarkable spine-bearing tubercles (fig. 10, B).
FIG. 50. - Tagiades sabadius. S. Africa.
the five-branched radial nervur?. of the forewing, the cylindrical hairy larva, and the pupa attached only by the cremaster. The Papilionidae are large butterflies with ample wings, and all six legs fully developed in both sexes. The forewing has five radial and two anal nervures, the second of the latter being free from the first and running to the dorsum of the wing, while the hindwing has but a single anal, and is frequently prolonged into a " tail " at the FIG. 58. - Papilio machaon (Swallow-tail). Europe.
third median nervure (fig. 58). The larva is cylindrical, never hairy but often tuberculate and provided with a dorsal retractile tentacle (osmaterium) on the prothorax. The pupa, which has a ,, ,,`?
FIG. 59. - Parnassius apollo (Apollo). European Alps.
double " nose-horn," is attached by the cremaster and a waistgirdle to the food-plant in the Papilioninae (fig. 58), but lies in a web on the ground among the Parnasiinae (figs. 59, 60). The latter subfamily includes the well-known Apollo butterflies of the Alps.
The former is represented in the British fauna by the East Anglian swallow-tail (Papilio machaon), and is very abundant in the warmer regions of the world, in cluding some of the most magnificent and brilliant of insects.
Agreeing with the Papilionidae in the six perfect legs of both sexes and the cincture-support of the pupa we find the Pieridae - the family of the white and yellow butterflies (figs. 61, 62) - represented by ten species in the British fauna and very widely spread over the earth's surface. In the Pieridae there are two anal nervures in the hindwing, while the second anal nervure in the forewing runs into the first; the larva is cylindrical and hairy without an osmaterium. The pupa has a single " nose-horn," and in the more highly organized genera there is no mobility whatever between its abdominal segments. The wintering pupae of the common cabbage butterflies (Pieris brassicae and P. rapae) are common objects attached to walls and fences and their colour harmonizes, to a great extent, with that of their surroundings.
The Nymphalidae are by far the largest and most dominant family of butterflies. In both sexes the forelegs are useless for walking (fig. 63), the tarsal segments being absent and the short shins clothed with long hairs, whence the name of brush-footed butterflies is often applied to the family. The neuration of the wings resembles FIG. 62. - A ppias nero (male). Malaya that found among the Pieridae, but in the Nymphalidae the pupa, which has a double nose-horn (fig. 65) - as in Papilio - is suspended from the cremaster only, no girdling thread being present, or it lies simply on the ground. The egg is elongate and sub-conical in form FIG. 64. - Larva of Argynnis paphia (Silver-washed Fritillary). Europe.
and ornamented with numerous ribs, while the larva is usually protected by numerous spines (fig. 64) arising from the segmental tubercles. To this family belong our common gaily-coloured butterflies - the tortoiseshells, peacock (fig. 65), admirals, fritillaries 7 After Grote, Natural Science, vol. 12 (J. M. Dent & Co.).
FIG. 55. - Neuration of Wings in Lycaena. 2, Sub-costal.
3, Radial.
4, Median.
5, Cubital.
7, 8, Anal nervures.
FIG. 56. - Eurybia carolina. Brazil FIG. 57. - Calephelis caenius. N. America.
FIG. 63. - Dione moneta. Brazil.
FIG. 61. - Colias hyale (Pale clouded Yellow Butterfly). Europe.
and emperors. In most cases the bright colouring is confined to the upper surface of the wings, the under-side being mottled and often inconspicuous. Most members of the group Vanessidi - the peacock and tortoiseshells (Vanessa) and the red admiral (Pyrameis) for FIG. 65. - Vanessa io (Peacock) and its pupa.
exampl
hibernate in the imaginal state. This large family is divided into several sub-families whose characters may be briefly given, as they are considered to be distinct families by many entomologists. The Danainae (or Euploeinae, fig. 66) have the anal nervures of the forewing arising from a common stalk, the discoidal areolets in both wings closed, and the front feet of the female thickened; their FIG. 66. - Euploea leucostictos (male). Malaya.
larvae are smooth with fleshy processes. The danaine butterflies range over all the warmer parts of the world, becoming most numerous in the eastern tropics, where flourish the handsome purple Euploeae whose males often have " brands " on the wings; these insects are conspicuously marked and are believed to be distasteful to birds and lizards. So are the South American Ithomiinae, distinguished from the Danainae by the slender feet of the females; the narrow winged, tawny Acraeinae, with simple anal nervures, thick hairy palps and spiny larvae; and the Heliconiinae whose palps are compressed, scaly at the sides and hairy in front. This a last named sub-family is confined to the Neotropical Region, while the Acraeinae are most numerous in the Ethiopian. The Nymphalinae include the British 5 vanessids (fig. 65), and a vast 6 assemblage of exotic genera (figs. 68, 70), characterized by the " open " discoidal areolets (fig. 67) owing to the absence of the transverse " disco-cellular " nervules. In the Morphinae - including some magnificent South American insects with deep or azure FIG. 70. - Callithea sapphira. Brazil.
blue wings, and a few rather. dull-coloured l, Oriental genera - the areolets are closed in the forewings and often in the hind wings. The larvae of the Morphinae (fig. 71) are smooth 7 After A. R. Grote, Natural Science, vol. 12 (J. M. Dent & Co.).
FIG. 67. - Neuration of Wings in a Nymphaline Butterfly.
2, Sub-costal.
3, Radial.
4, Median.
5, Cubital.
6, 7, 8, Anal nervures.
FIG. 68. - Nymphalis jason. W. Africa. Upper and under surface.
FIG. 69. - Larva and Pupa of Apatura ilia. or hairy with a curiously forked tail-segment. A similar larva characterizes the South American Brassolinae or owl-butterflies - FIG. 71. - Larva of Amathusia phidippus. FIG. 72. - Opsiphanes syme. Brazil.
FIG. 73. - Brassolis astyra. Brazil.
After A. R. Grote, Natural Science, vol.
iz (J. M. Dent & Co.).
FIG. 74. - Neuration of wings in Pararge, a satyrid butterfly.
2, Sub-costal.
3, Radial.
4, Median.
5, Cubital.
7, 8, Anal nervures. FIG. 76 - Bia actorion. Brazil.
robust insects (figs. 72, 73) with the areolets closed in both wings, which are adorned with large " eye-spots " beneath. The Satyrinae, including our native browns and the Alpine Erebiae, resemble the foregoing group in many respects of structure, but the sub-costal nervure is greatly thickened at the base (fig. 74). This sub-family is world-wide in its distribution. One genus (Oeneis, fig. 75) is found in high northern latitudes, but reappears in South America. The dark, spotted species of Erebia are familiar insects to travellers among the Alps; yet butterflies nearly related to these Alpine insects occur in Patagonia, in South Africa and in New Zealand. Such facts of distribution clearly show that though the Nymphalidae have attained a high degree of specialization among the Lepidoptera, some of their genera have a history which goes back to a time when the distribution of land and water on the earth's surface must have been very different from what it is to-day.
Bibliography. - The handsome Lepidoptera, with their interesting and easily observed life-histories, have naturally attracted many students, and the literature of the order is enormous. M. Malpighi's treatise on the anatomy of the silkworm (De Bombycibus, London, 1669) and P. Lyonnet's memoir on the Goat-caterpillar, are among the earliest and most famous of entomological writings. W. F. Kirby's Handbook to the Order Lepidoptera (5 vols., London, 1894-1897) should be consulted for references to the older systematic writers such as Linnaeus, J. C. Fabricius, J. Hubner, P. Cramer, E. Doubleday and W. C. Hewitson. Kirby's Catalogues are also invaluable for the systematist. For the jaws of the Lepidoptera see F. Darwin, Quart. Journ. Mic. Sci. xv. (1875); E. Burgess, Amer. Nat. xiv. (1880); A. Walter, Jen. Zeits. f. Naturw. xviii. (1885); W. Breitenbach, Ib. xv. (1882); V. L. Kellogg, Amer. Nat. xxix. (1895). The last-named deals also with wing structure, which is further described by A. Spuler, Zeits. wiss. Zool. liii. (1892) and Zool. Jahrb. Anat. viii. (1895); A. R. Grote, Mitt. aus dem RoemerMuseum (Hildesheim, 1896-1897); G. Enderlein, Zool. Jahrb. Anat. xvi. (1903), and many others. For scales see A. G. Mayer, Bull. Mus. Comp. Zool. Harvard, xxix. (1896). For internal anatomy W. H. Jackson, Trans. Linn. Soc. Zool. (2) v. (1891), and W. Petersen, Mem. Acad. Imp. Sci. St Petersburg (8) ix. (1900). The early stages and transformations of Lepidoptera are described by J. Gonin, Bull. Soc. Vaud. Sci. Nat. xxx. (1894); E. B. Poulton, Trans. Linn. Soc. Zool. (2) v. (1891); H. G. Dyar, Ann. New York Acad. Sci. viii. (1894); T. A. Chapman, Trans. Entom. Soc. Lond. (1893), &c. For habits and life-relations see A. Seitz, Zool. Jahrb. Syst. v., vii. (1890, 1894); A. Weismann, Studies in the Theory of Descent (London, 1882) and Entomologist, xxix. (1896); F. Merrifield, Trans. Entom. Soc. Lond. (1890, 1893, 1905); M. Standfuss, Handbuch der paldarktischen Gross-schmetterlinge (Jena, 1896); R. Trimen, Proc. Ent. Soc. Lond. (1898); E. B. Poulton, Colours of Animals (London, 1890); Trans. Entom. Soc. (1892 and 1903), and Journ. Linn. Soc. Zool. xxvi. (1898); F. E. Beddard, Animal Coloration (London, 1892). For distribution see H. J. Elwes, Proc. Entom. Soc. Lond. (1894); J. W. Tutt, Migration and Dispersal of Insects (London, 1902); Fossil Lepidoptera, S. H. Scudder, 8th Rep. U.S. Geol. Survey (1889). Among recent general works on the Lepidoptera, most of which contain numerous references to the older literature, may be mentioned A. S. Packard's unfinished work on the Bombycine Moths of N. America, Mem. Nat. Acad. Sci. Philadelphia, vii. (1895), and Mem. Acad. Sci. Washington, lx. (1905); D. Sharp's chapter in Cambridge Nat. Hist. vi. (London, 1898); G. F. Hampson, Moths of India (4 vols., London, 1892-1896), and Catalogue of the Lepidoptera Phalaenae (1895) and onwards; S. H. Scudder, Butterflies of New England (3 vols., Cambridge, Mass., 1888-1889); W. J. Holland, Butterfly Book (New York, 1899). Works on the British Lepidoptera are numerous, for example, those of H. T. Stainton (1851), C. G. Barrett (1893-1907), E. Meyrick (1895), and J. W. Tutt (1899 and onwards). For recent general systematic works, the student should consult the catalogues mentioned above and the Zoological Record. The writings of O. Staudinger, E. Schatz, C. Oberthiir, K. Jordan, C. Aurivillius and P. Mabille may be specially mentioned.
(G. H. C.)
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Bibliography Information
Chisholm, Hugh, General Editor. Entry for 'Lepidoptera'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/l/lepidoptera.html. 1910.
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