Chapter XIX: Act 1867: every British ship going to other countries where lemon or (10)

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.

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.

FIG. 14.--Clothes Moth (_Tinea pellionella_), with larva in and out of its case. Magnified.]

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. 14), for example, make a tubular dwelling out 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.

FIG. 16.--Pupa of Gypsy Moth (_Porthetria dispar_) sheltered in leaves joined by silken threads. Below is the cast larval cuticle.]

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 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. 11, 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 wing-patterns 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 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.

_Distribution and Migration._--The range of the Lepidoptera is practically world-wide; they are absent from the most remote and inhospitable of the arctic and antarctic lands, but even Kerguelen possesses a few small indigenous moths. Many of the large and dominant families have a range wide as that of the order, and certain species that have attached themselves to man--like the meal moths and the clothes moths--have become almost cosmopolitan. Interesting and suggestive restrictions of range can, however, be often traced. Although butterflies have been found in 82° N. latitude in Greenland, they are unknown in Iceland, and only a few species of the group reach New Zealand. Three large sections--the Ithomiinae, Heliconiinae and Brassolinae--of the great butterfly family Nymphalidae are peculiar to the Neotropical region, while the Morphinae, a characteristically South American group, have a few Oriental genera in India and Indo-Malaya. The Acraeinae, another section of the same family, have the vast majority of their species in Ethiopian Africa, but are represented eastwards in the Oriental and Australian regions and westwards in South America. A comparison of the lepidopterous faunas of Ireland, Great Britain and the European continent is very instructive, and suggests strongly that, despite their power of flight the Lepidoptera are mostly dependent on land-connexions for the extension of their range. For example, Ireland has only forty of the seventy species of British butterflies. The range of many Lepidoptera is of course determined by the distribution of the plants on which their larvae feed.

Nevertheless certain species of powerful flight, and some that might be thought feeble on the wing, often cross sea-channels and establish or reinforce distant colonies. Caterpillars of the great death's head moth (_Acherontia atropos_) are found every summer feeding in British and Irish potato fields, but it is doubtful if any of the pupae resulting from them survive the winter in our climate. It is believed by Tutt that the species is only maintained by a fresh immigration of moths from the South each summer. Hosts of white butterflies (_Pieris_) have been frequently observed crossing the English Channel from France to Kent. Migrating swarms of Lepidoptera have often been met by sailors in mid-ocean; thus, Tutt records the presence around a sailing ship in the Atlantic of such a swarm of the rather feeble moth _Deiopeia pulchella_, nearly 1000 m. from its nearest known habitat. This migratory instinct is connected with the gregarious habits of many Lepidoptera. For example, H. W. Bates states that at one place in South America he noticed eighty different species flying about in enormous numbers in the sunshine, and these, with few exceptions, were males, the females remaining within the forest shades. Darwin describes a "butterfly shower," which he observed 10 m. off the South American coast, extending as far as the eye could reach; "even by the aid of the telescope," he adds, "it was not possible to see a space free from butterflies." Sir J. Emerson Tennent, witnessed in Ceylon a mighty host of butterflies of white or pale yellow hue, "apparently miles in breadth and of such prodigious extension as to occupy hours and even days uninterruptedly in their passage." Observations at Heligoland by H. Gätke have shown that migrating moths "travel under the same conditions as migrating birds, and for the most part in their company, in an east to west direction; they fly in swarms, the numbers of which defy all attempts at computation and can only be expressed by millions." The painted lady butterfly (_Pyrameis cardui_) comes in repeated swarms from the Mediterranean region into northern and western Europe, while in North America companies of the monarch (_Anosia archippus_) invade Canada every summer from the United States, and are believed to return southwards in autumn. This latter species has, during the last half-century, extended its range south-westwards across the Pacific and reached the Austro-Malayan islands, while several specimens have occurred in southern and western England, though it has not established itself on this side of the Atlantic. It is noteworthy that the introduction of its food-plant--_Asclepias_--into the Sandwich Islands in 1850 apparently enabled it to spread across the Pacific.

_Fossil History._--Our knowledge of the geological history of the Lepidoptera is but scanty. Certain Oolitic fossil insects from the lithographic stone of Solenhofen, Bavaria, have been described as moths, but it is only in Tertiary deposits that undoubted Lepidoptera occur, and these, all referable to existing families, are very scarce. Most of them come from the Oligocene beds of Florissant, Colorado, and have been described by S. H. Scudder. The paucity of Lepidoptera among the fossils is not surprising when we consider the delicacy of their structure, and though their past history cannot be traced back beyond early Cainozoic times, we can have little doubt from the geographical distribution of some of the families that the order originated with the other higher Endopterygota in the Mesozoic epoch.

_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 suborder _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 suborder _Laciniata_, all the rest of the order forming the suborder _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 jugum near the
base of the wing, and the neuration of the hindwing is closely like
that of the forewing, the radial nervure being five-branched 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 Jugatae--are
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. 1),
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 wing-neuration is of
the primitive tineoid type; the smooth larvae feed on the stems or
roots of plants and the pupal structure agrees with that of the
Tortricidae and 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 family of brownish nocturnal moths, allied to the
Zygaenidae and agreeing with them in the 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 plants. The
pupa, with three or four free abdominal segments, remains 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
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 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 _Plutellidae_ (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 food-plant (_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 sub-costal nervure bends towards and often
connects with the radial, and the frenulum is 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
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
kühniella_ (fig. 30), become serious pests in storehouses and
granaries, their larvae devouring flour and similar food-stuffs.

FIG. 30.--Flour Moth (_Ephestia kühniella_).

c, With wings spread.
f, At rest.
g, h, i, Marking and neuration of wings.
a, Larva.
b, Pupa.
d, Head and front body-segments of larva.
e, 2nd and 3rd abdominal segments.]

_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
ana 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 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_, distinguished from the
"tussocks" by the slender upturned terminal segment of the labial
palps and by the development of the maxillae.

FIG. 34.--e, f, _Heliothis armigera._ Europe, c, Larva; d, pupa in
cell. Natural size. a, b, Egg, highly magnified.]

The _Noctuidae_ are the largest and most dominant family of the
Lepidoptera, comprising some 10,000 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 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 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._

FIG. 38.--c, Tiger Moth (_Phragmatobia fuliginosa_, Linn.). Europe. a,
Caterpillar; b, cocoon with pupa. Slightly enlarged.]

This group includes a series of families which agree with the
Noctuides in most points, but are distinguished by the origin of the
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 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
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_. 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 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 resemblance both in form
and colour to the twigs of their food-plant. 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 exquisite 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.

FIG. 43.--Geometrid Moth (_Amphidasys betularia_, Linn.). Europe. a,
Large grey type; b, dark variety; c, caterpillar in looping attitude.]

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. 46b). 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 _Acherontia atropos_ and _Protoparce
convolvuli_--migrate into the British Islands in numbers almost every
summer.

A group of families in which the first maxillae are vestigial, the
feelers bipectinate and the pupa enclosed in a dense silken cocoon,
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 cocoon-spinning 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 the larvae are
smooth, with some of the segments humped and the eighth abdominal
often carrying a dorsal spine. The family is tropical in its
distribution, but the common silkworm (_Bombyx mori_, fig. 48) has
become acclimatized in southern Europe and is the source of most of
the silk used in manufacture and art. Of commercial value also is the
silk spun by the great moths of the family _Saturniidae_, well
represented in 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 caterpillars are protected by remarkable
spine-bearing tubercles (fig. 10, B).

FIG. 48.--_Bombyx mori._ China. a, Caterpillar (the common silkworm);
b, cocoon; c, male moth.]

_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 these have 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
"head-piece" or "nose-horn" to protect the head-region of the
contained 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 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 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, the five-branched radial nervure of
the forewing, the cylindrical hairy larva, and the pupa attached only
by the cremaster.

FIG. 55.--Neuration of Wings in _Lycaena_.

2, Sub-costal.
3, Radial.
4, Median.
5, Cubital.
7, 8, Anal nervures.]

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 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 double
"nose-horn," is attached by the cremaster and a waist-girdle 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 sub-family
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, including 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.

FIG. 67.--Neuration of Wings in a Nymphaline Butterfly.

2, Sub-costal.
3, Radial.
4, Median.
5, Cubital.
6, 7, 8, Anal nervures.]