The Castnia of South America are many of them like Nymphalid butterflies, but exhibit great diversity, and resemble butterflies of several different divisions of the family.[[239]]
The species are apparently great, lovers of heat and can tolerate a very dry atmosphere.[[240]] The transformations of very few have been observed; so far as is known the larvae feed in stems; and somewhat resemble those of Goat-moths or Leopard-moths (Cossidae); the caterpillar of C. therapon lives in the stems of Brazilian orchids, and as a consequence has been brought to Europe, and the moth there disclosed. The pupae are in general structure of the incomplete character, and have transverse rows of spines, as is the case with other moths of different families, but having larvae with similar habits.[[241]] Castnia eudesmia forms a large cocoon of fragments of vegetable matter knitted together with silk. These Insects are rare in collections; they do not ever appear in numbers, and are generally very difficult to capture.
Fam. 2. Neocastniidae.—The Oriental genus Tascina, formerly placed in Castniidae has recently been separated by Sir G. Hampson and associated with Neocastnia nicevillei, from East India, to form this family. These Insects have the appearance of Nymphalid butterflies. They differ from Castniidae by the want of a proboscis.
Fam. 3. Saturniidae.—This is a large and varied assemblage of moths; the larvae construct cocoons; the products of several species being used as silk. These moths have no frenulum and no proboscis. The hind wings have a very large shoulder, so that the anterior margin or costa stretches far forward beneath the front wing, as it does in butterflies. The antennae of the males are strongly bipectinated and frequently attain a magnificent development. The family includes some of the largest and most remarkable forms of the Insect-world, Coscinocera hercules, inhabiting North Australia, is a huge moth which, with its expanded wings and the long tails thereof, covers a space of about 70 square inches. One of the striking features of the family is the occurrence in numerous forms of remarkable transparent spaces on the wings; these window-like areas usually occur in the middle of the wing and form a most remarkable contrast to the rest of the surface, which is very densely scaled. In Attacus these attain a large size. In other species, such as the South African Ludia delegorguei, there is a small letter-like, or symboliform, transparent mark towards the tip of each front wing. We have at present no clue to the nature or importance of these remarkable markings. In the genus Automeris, and in other forms, instead of transparent spaces there are large and staring ocellate marks or eyes, which are concealed when the Insect is reposing. In Arceina, Copiopteryx, Eudaemonia and others, the hind wings are prolonged into very long tails, perhaps exceeding in length those of any other moths.
Fig. 187—Larva of Attacus atlas, India. A, at end of 1st instar, profile; B, 4th instar, dorsal view; C, full-grown larva, in repose. (After Poujade.)
The cocoons are exceedingly various, ranging from a slight open network to a dense elaborate structure arranged as in our Emperor moth; in this latter case an opening is left by the larva for its exit after it has become a moth, but by an ingenious, chevaux-de-frise work, this opening is closed against external enemies, though the structure offers no resistance at all to the escape of the moth. Fabre has recorded some observations and experiments which seem to show that the instinct predominating over the formation of the cocoon is not cognoscent. The Insect, if interfered with, displays a profound stupidity. Its method is blind perseverance in the customary.[[242]] The cocoon of Saturniidae is more often continuous, i.e. entirely closed. Packard says that Actias luna effects its escape by cutting through the strong cocoon with an instrument situate at the base of the front wing. Other species were examined and were found to possess the instrument; but Packard is convinced that the majority of the species possessing the instrument do not use it, but escape by emitting a fluid that softens the cocoon and enables the moth to push itself through.[[243]] The cocoons of the species of Ceranchia have a beautiful appearance, like masses of filagree-work in silver. The pupa in Ceranchia is very peculiar, being terminated by a long, spine-like process. In Loepa newara the cocoon is of a green colour and suspended by a stalk; looking like the pod, or pitcher, of a plant. The silk of the Saturniidae is usually coarse, and is known as Tusser or Tussore[[244]] silk.
The larvae of this family are as remarkable as the imagos, being furnished with spine-bearing tubercles or warts, or long fleshy processes; the colours are frequently beautiful. The caterpillar of Attacus atlas (Fig. 187) is pale olive-green and lavender, and has a peculiar, conspicuous, red mark on each flank close to the clasper.
About seventy genera and several hundred species are already known of this interesting family. They are widely distributed on the globe, though there are but few in Australia. Our only British species, the Emperor moth, Saturnia pavonia, is by no means rare, and its larva is a beautiful object; bright green with conspicuous tubercles of a rosy, or yellow, colour. It affects an unusual variety of food-plants, sloe and heather being favourites; the writer has found it at Wicken flourishing on the leaves of the yellow water-lily. Although the Emperor moth is one of the largest of our native Lepidopterous Insects, it is one of the smallest of the Saturniidae.
The family Hemileucidae of Packard is included at present in Saturniidae.