656 POPULAR SCIENCE MONTHLY. 



THE CASE MOTHS. 



By MAKGAKET T. D. BADENOCH. 



IT seems an incontrovertible fact in natural history tliat tliere is 

 not a single character which has been used to distinguish any 

 group of considerable extent from which some one or more of the 

 members thereof may not depart. In that great division of the 

 animal kingdom characterized by the possession of articulated limbs, 

 many species are met which are entirely wanting in those organs, 

 and, similarly, the secondary division of the Armulosa, marked by the 

 presence of wings in the final state — the Ptilota of Aristotle — con- 

 tains species that, throughout life, never acquire instruments of 

 flight. Of wingless insects, indeed, examples might be drawn from 

 most of the orders, and in the majority of cases the females only 

 are thus deprived. Rarely, however, both the great characteristics 

 are absent. Yet certain moths do not possess articulated feet in the 

 wingless state. 



Consequently, if we took into consideration merely the adults 

 of these females, this group must be regarded as among the most 

 degraded instances of apiropodous insects. But such a conclusion 

 can not be maintained, as shown by an examination of the early 

 stages of the moths, for these, w^e find, exhibit as high an amount 

 of organization as those of any of the other insects appertaining to 

 the order. The truth is, these females have become degenerate — 

 very different from the creatures they once were. Their peculiarity 

 consists in this, that whereas, as a whole, winged insects always 

 undergo a gradual evolution of structure, by which ultimately legs 

 and wings are developed, these individuals gradually lose their 

 powers of evolution, and not only this, but suft'er a process of de- 

 terioration, by which the limbs which they at first possess diminish, 

 and at length dwindle altogether away, until the animal becomes a 

 mere short, inert vermiform bag, having not only no distinct trace 

 of legs and wings, but also the sense-organs, the antenna?, and the 

 organs of the mouth are almost or entirely obliterated, and even the 

 articulated condition of the body has almost disappeared. In these 

 extreme forms it is hardly possible for the degeneration of the 

 female to proceed further, and in all, doubtless, the change has occu- 

 pied an immense period. 



Than these extraordinary moths, familiar to German entomolo- 

 gists under the name of Sacktrdgers, perhaps no more curious and 

 interesting examples occur among the whole of the insect races; cer- 

 tainly in structure of the female, and in habit, they are the strangest 

 and most abnormal of all Lepidoptei'a. They belong to the Psychidce, 



