Fig. 177.—Pupa of the Purple Emperor butterfly, Apatura iris. New Forest. A, Lateral, B, dorsal aspect; C, enlarged view of cremaster with the suspensory hook; D, one hook still more enlarged.
Sub-Fam. 1. Danaides.—Front wing with inner-margin (submedian) nervure, with a short fork at the base. Cell of hind wing closed. Front foot of the female ending in a corrugate knob. Caterpillars smooth, provided with a few long fleshy processes. The claws are in a variable state, being sometimes simple, as in Papilionidae, sometimes with an empodium, apparently of an imperfect kind. The Danaides are usually large Insects with an imperfect style of ornament and colour; they have a great deal of black or very dark scaling, and in some Euploea this is agreeably relieved by a violet or purple suffusion, and these are really fine Insects. Usually there are large pale spaces, of some neutral indefinite tint, on which black blotches are distributed in a striking but inartistic manner. In many of the species the markings are almost spot for spot the same on the upper and under sides. About seven genera and 250 species are recognised. Danaides occur in all the warmer parts of the world, but are most numerous in the Eastern tropics. In Europe the family is represented only by an Asiatic and African species, Limnas chrysippus, that has extended its range to Greece. Besides this another species, Anosia erippus, Cr. (unfortunately also called Anosia menippe, Hb., and Danais archippus or even D. plexippus) has in the last two or three decades extended its range to various islands and distant localities, concomitantly, it is believed, with an extension of the distribution of its food-plant, Asclepias. This Insect has several times been taken in this country, and may probably be a natural immigrant. It is a common butterfly in North America, where it is called the Monarch.[[214]]
Some, at least, of the Danaides are unpleasant to birds in odour or in taste, or both. Among them there occur, according to Moore[[215]] and others, numerous cases of resemblance between forms that are thus protected. It is possible that the odour and taste are of some value to the Insects;[[216]] as, however, butterflies of any kind appear to be but rarely attacked in the imago-state by birds, and as their chief enemies are parasitic Insects that attack the larval instar, it is impossible to consider this protection of such prime importance to the species as many theorists assume it to be.
Fig. 178—Ithomia pusio. Brazil.
Sub-Fam. 2. Ithomiides.—Differs from Danaides by the female front foot having a true, though somewhat abbreviate tarsus. The caterpillers have no long processes. There has been considerable difference of opinion as to this division of butterflies. It is the family Neotropidae of Schatz, the Mechanitidae of Berg; also the "Danaioid Heliconiidae" of several previous writers, except that Ituna and Lycorea do not belong here but to Danaides. Godman and Salvin treat it as a group of the Danaid sub-family. The Ithomiides are peculiar to tropical America, where some 20 or 30 genera and about 500 species have been discovered. There is considerable variety amongst them. Ithomia and Hymenitis are remarkable for the small area of their wings, which bear remarkably few scales, these ornaments being in many cases limited to narrow bands along the margins of the wings, and a mark extending along the discocellular nervule. Wallace says they prefer the shades of the forest and flit, almost invisible, among the dark foliage. Many of these species have the hind-wings differently veined in the two sexes on the anterior part, in connection with the existence in the male of peculiar fine hairs, placed near the costal and subcostal veins. Tithorea and other forms are, however, heavily scaled insects of stronger build, their colours usually being black, tawny-red or brown, yellow, and white. In the sub-fam. Danaides, according to Fritz Müller, the male has scent-tufts at the extremity of the abdomen, whereas in Ithomiides analogous structures exist on the upper side of the hind-wing. Ithomiides have various colour-resemblances with members of the Heliconiides and Pieridae; Tithorea has colour analogues in Heliconius, and Ithomia in Dismorphia (formerly called Leptalis). Crowds of individuals of certain species of Ithomia are occasionally met with, and mixed with them there are found a small number of examples of Dismorphia coloured like themselves. They are placed by Haase in his category of secondary models. Belt states that some Ithomiides are distasteful to monkeys and spiders, but are destroyed by Fossorial Hymenoptera, which use the butterflies as food for their young; and he also says that they are very wary when the wasp is near, and rise off their perches into the air, as if aware that the wasp will not then endeavour to seize them. Much information is given about the habits by Bates in the paper in which he first propounded the "theory of mimicry."[[217]] The larvae are said to live on Solanaceae.
The genus Hamadryas is placed by some writers in Danaides, by others in Ithomiides; and Haase has proposed to make it the group "Palaeotropinae." The species are small, black and white Insects, somewhat like Pierids. They are apparently hardy Insects, and are abundant in certain parts of the Austro-Malay region.
Sub-Fam. 3. Satyrides.—Palpi strongly pressed together, set in front with long, stiff hairs. Front wings frequently with one or more of the nervures swollen or bladder-like at the base of the wing. Cells of both wings closed. Caterpillar thickest at the middle, the hind end of the body bifid. Pupa generally suspended by the cremaster, without girth: but sometimes terrestrial. This is a very extensive group, consisting of upwards of 1000 species. The Insects are usually of small size, of various shades of brown or greyish colours, with circular or ringed marks on the under sides of the wings. It is found all over the world, and is well represented in Europe; our Meadow-browns, Heaths, and Marbled-whites, as well as the great genus Erebia of the highlands and mountains belonging to it. Most of these Insects have but feeble powers of flight, and rise but little from the surface of the ground. The caterpillars live on various grasses. They are usually green or brown, destitute of armature, and a good deal like the caterpillars of Noctuid moths, but the hind end of the body is thinner and divided to form two corners, while the head is more or less free, or outstanding. The pupae are of great interest, inasmuch as in a few cases they do not suspend themselves in any way, but lie on the ground; sometimes in a very feeble cocoon or cell. There are no cremasteral hooks. The pupae of the Grayling butterfly, Hipparchia semele, has been found in loose soil a quarter of an inch below the surface. The chrysalis of the Scotch Argus, Erebia aethiops, was found by Mr. Buckler to be neither suspended nor attached, but placed in a perpendicular position, head upwards, amongst the grass. In the majority of cases the pupa is, however, suspended as is usual in Nymphalidae. Nothing is known as to the nature of the peculiar inflation of the bases of the nervures of the front wings; it is well shown in our common species of Coenonympha; this character is not, however, constant throughout the family. There is in South America a very remarkable group of Satyrides consisting of the genera Cithaerias and Haetera, in which the wings are very delicate and transparent, bearing on the greater part of their area remote fine hairs instead of scales; there are nevertheless some scaled patches about the margins, and one or more of the ringed marks characteristic of the Satyrides; while in some species the distal portions of the hind wings are tinted with carmine. The species of the genus Pierella connect these transparent Satyrids with the more ordinary forms. According to Wallace the habits of these fairy-like forms are those characteristic of the family in general. The genus Elymnias has been separated by some authorities as a sub-family, or even as a family, Elymniidae, chiefly on the ground of a slight peculiarity in the termination of the branches of the veins at the outer angle of the front wings. The Elymnias are said to be of a mimetic nature, having a greater or less resemblance to butterflies of various other divisions; there is also a considerable difference in appearance between their own sexes. The larva of E. undularis is known; it is of the form usual in Satyrides, and lives on the palm Corypha. About 50 species, ranging from India to Australia, with two in Africa, are known of this interesting group.
Sub-Fam. 4. Morphides.—There is no cell on the hind wing, the discocellular nervule being absent (Fig. 161, II. B). Caterpillars smooth or spiny, with the extremity of the body divided; frequently gregarious. These Insects have become notorious from the extraordinary brilliancy of blue colour exhibited by the upper surface of the wings of the typical genus Morpho. The species of Morpho are all Insects of large size, but with wings enormous in proportion to the body; this latter part is carried in a sort of cradle formed by the inner parts of the margins of the hind wings. Although an arrangement of this kind is seen in numerous other butterflies, yet there is perhaps none in which it is carried to quite such a pitch of perfection as it is in Morpho, where, on the under surface no part of the body behind the posterior legs can be seen. There are only about 100 species of Morphides, and 50 of these are included in Morpho, which is peculiar to tropical and sub-tropical America; the other half of the family is divided among ten or twelve genera, found in the Indo-Malay region; there being none in Africa. The eastern Morphides, though fine Insects, are not to be compared, either in size or brilliancy, with their American allies. The species of Morpho are apparently found only in the great forests of South America, where they are far from rare; some have a flapping and undulating flight, straight onwards along the alleys of the forest, and near the ground; others are never seen except steadily gliding with outstretched wings from 20 to 100 feet above the ground, where they move across sunny spaces between the crowns of the taller trees; the low-flyers settle frequently on the ground to suck the juices from fallen fruit, but the members of the other section never descend to the ground. As regards the caterpillars, W. Müller tells us[[218]] that the spines they are armed with break off, and enter the skin, if the creatures are carelessly handled. Four of the five species known to him are conspicuously coloured with black, red, yellow and white. The individuals are gregarious. The larvae of M. achilles sit in companies, often of more than 100 individuals, on trunks of trees, and so form a conspicuous patch. The caterpillars of M. epistrophis hang together as red clumps on the twigs of their food-plants. Hence it appears that in this genus we have an exception to the rule that night-feeding caterpillars rest in a hidden manner during the day.