Fam. 18. Heterogynidae.—Consists of the single genus Heterogynis which has hitherto been found only in the south of Europe. This is an important form connecting Zygaenidae and Psychidae. The larvae resemble those of Zygaena, and construct an oval cocoon for their metamorphosis. The male issues as a small moth of smoky colour, the scales being but imperfect; the female chrysalis shows no trace of any appendages, and the imago is practically a maggot, and never leaves the cocoon; in it she deposits her eggs, and the young larvae hatch there.[[275]]
Fam. 19. Psychidae.—Small, or moderate-sized moths, with imperfect scales, and little or no colour beyond certain shades of duskiness; the sexes very different, the female being wingless and sometimes quite maggot-like; the male often with remarkable, bipectinate antennae, the branches sometimes very long and flexible. Larva inhabiting a case that it carries about. This family consists of Insects unattractive in appearance but presenting some points of great interest. It is frequently stated that the Psychidae are destitute of scales, but Heylaerts states[[276]] that, in addition to hairs, scales of a more or less imperfect formation are present in all, but that they are, like those of some Sphingidae (Macroglossa), very easily detached. There is much difference in the females, some having well-developed legs, while others are not only apterous, but are bare and destitute of appendages like a maggot, while in certain cases (Fig. 196, G), the head is reduced in size and is of peculiar form so as to make the Insect look really like the larva of one of the parasitic Diptera. These females never leave their cases, but deposit their eggs therein, and inside, also, their former pupa-skin; and here the young hatch; the peculiar little larvae are very numerous, and it is suggested that they make a first meal on the body of their parent, but this we believe has not been satisfactorily ascertained. Great differences as to the condition of the legs, antennae, etc., are said to exist in species of the same genus. There is also a remarkable diversity in the pupae of the females; the male sex being normal in this respect. Some of the female pupae are destitute of wing-sheaths and all other appendages, while others are said to possess them, though there are no wings at all in the imago (Fumea, e.g.).[[277]] Great difficulties attend the study of these case-bearing Insects, and several points require careful reconsideration, amongst them the one we have just mentioned. The males fly rapidly in a wild manner, and may sometimes be met with in swarms; their lives are believed to be very brief, rarely exceeding a couple of days, and sometimes being limited to a few hours.
Fig. 196—Metamorphosis of Monda rhabdophora. Ceylon. A, Larva in case, nat. size; B, larva itself, magnified; C, case of female during pupation; D, case of male during pupation; E, female pupa, magnified; F, male moth, nat. size; G, female moth, magnified. (From unpublished drawings by Mr. E. E. Green).
The larvae are called basket-worms, and their baskets or cases are well worthy of attention. Their variety is remarkable; the most extraordinary are some of the genus Apterona Fig. 197, B, which perfectly resemble the shells of Molluscs such as snails; indeed, the specimens in the collection at the British Museum were sent there as shells. This case is not, like those of other Psychidae, constructed of earth or vegetable matter, but is of silk and is in texture and appearance exactly like the surface of a shell. Psyche helix is, according to Ingenitzky,[[278]] found in great numbers near Lake Issyk-kul in Central Asia, where the larvae feed, in their snail-shell-like cases, on a grass, just like snails. Only females could be reared from these larvae. The case of Chalia hockingi (Fig. 197, C) consists of little pieces of wood cut to the proper lengths, and spirally arranged, so as to form a construction that would be quite a credit to our own species. In some of the Canephorinae we meet with long cylindrical cases, like those of Caddis-worms, or of Tineid larvae.
Fig. 197—Baskets, or cases, of Psychidae. A, Amicta quadrangularis; B, Apterona (or Cochlophora) valvata; C, Chalia hockingi.
Riley has given an account of several points in the structure and natural history of one of the North American basket- or bag-worms, Thyridopteryx ephemeraeformis; one of his points being the manner in which the newly hatched larva forms its case.[[279]] This question has also been discussed by Packard.[[280]] The larvae when hatched in unnatural conditions will make use of fragments of paper, cork, etc., for the case; the act of construction takes one or two hours, and the larva does not eat till the case is completed. It walks in a peculiar manner, the legs of the third pair being moved forwards together, as if they were the prongs of a fork.
This family is already one of considerable extent, but its study, as already remarked, is but little advanced. Some naturalists are inclined to place it among the Tineidae, but it is connected with Zygaenidae by means of Heterogynidae. Mr. Meyrick divides it, placing Psyche and Sterrhopteryx (the forms representing, according to his ideas, the family Psychidae in Britain) in the series Psychina which includes Zygaenidae. He removes the other British genera, Fumea, and Epichnopteryx, to Tineidae near Solenobia and Taleporia. The group Canephorinae, to which the two genera in question belong, was long since separated from Psychidae by Herrich-Schäffer, but this course was condemned by Heylaerts. Parthenogenesis has been thought by some to occur in numerous species in this family, but Heylaerts says that it is limited to Apterona crenulella var. helix, and even of this species males are found in certain localities.
Fam. 20. Cossidae (Goat-Moths, or Carpenter-Worms).—Moths of moderate, or rather large size, without proboscis, frequently with a dense covering of matted, imperfect scales; the pattern being vague. The larvae bore into trees in which they often make large burrows, leaving holes from which sap exudes. Our common Goat-moth is a good specimen of this family, which is a very widely distributed one. The Australian genus Ptilomacra has very large, pectinated antennae in the male. The larvae of Cossidae are nearly bare of clothing and are unadorned; they form a slight cocoon of silk mixed with gnawed wood. The pupa of the Goat-moth is remarkable for the great development of the rows of teeth on the dorsal aspects of the segments of the abdomen, and for the absence of consolidation in this part, six of the intersegmental incisions being free, and the ventral aspect almost membranous. Very little is known as to other pupae of the family. It is believed that the generations of these Insects are fewer than usual, the growth of the larva occupying a period of two or three years. The larva of Zeuzera aesculi forms a temporary cocoon in which it passes a winter-sleep, before again feeding in the spring.[[281]] It is a moot question whether the Zeuzeridae should be separated from the Cossidae or not. The group includes our Wood-leopard moth, which, like many other Zeuzerids, is spotted in a very striking but inartistic manner. The position the family Cossidae should occupy in an arrangement of the Lepidoptera is a very difficult question. Some consider the Insects to be allied to Tortricidae. The wing-nervuration of Cossus is very peculiar and complex, there being four or five cells on the front wing, and three on the hind one. Meyrick places Zeuzeridae as a family of his series Psychina, but separates Cossidae proper (he calls them Trypanidae) as a family of the series Tortricina.