72. 



The Naturalist. 



that it was merely a freak of nature in the intestinal matter, and no 

 distinction of sex or variety whatever. One dark brown ovum reveals 

 a male imago, another dark ovum a female ; and so with the other 

 colour — one may produce a male moth, another a female. Whether 

 the difference of colour is attributable to weakness on the part of the 

 male or female, collectively or singly, it is not for me to presume on 

 an opinion : I should be glad to hear naturalists' " public opinion '' 

 on the matter. Young caterpillars are the most precocious and pug- 

 nacious, but with their increasing size and age I am glad to say their 

 common sense, or common instinct, also developes. I have observed, 

 in breeding this larva, that often a " puss,'' which seemed (a very 

 short time ago) to have been in a healthy condition, sickens and 

 dies, and that very speedily. I am led to imagine that some kind of 

 an epidemic, or fever, inaugurated by that single one, has spread 

 through the whole brood, and death has carried them away conse- 

 quently. But some day I may be able to tackle the subject with 

 more solid foundation for my surmises than at present I possess. 



A caterpillar's life seems to be one continuous routine of changing 

 skins, and no sooner is one discarded than another appears on the 

 horizon, first as a dainty, delicate covering, then gradually becoming 

 stronger and healthier at every turn. Casting off one skin and 

 assuming another must by no means be confounded with the meta- 

 morphosis it undergoes during the last stage of existence, as, 

 comparatively speaking, one is but a slight operation — a day's work ; 

 the other is the work of a whole lifetime. I believe most animals of 

 the creeping class at some period of their lives throw off or change 

 their skins. Of course they, like Vinula, have their growth forcibly 

 circumscribed during the period they remain in the original covering. 

 Thus, for instance, "puss.'' It grows until a certain period, 

 when every point of the envelopment is stretched to the uttermost 

 pitch — then the skin, being unable to meet the exorbitant demands 

 of its interior members, whose faculties (at most other times dormant) 

 are always accessible to the cry, " Food !" must of necessity burst, a 

 new encasement having been previously matured. The cast-off skins, 

 withered and contemned^ fold up similarly to the slides of a telescope 

 — " wheels within wheels," in fact—though often a skin may be 

 discovered almost perfect in exterior and form. Indeed, I have 

 somewhere read that all the parts of the head, even to the skull and 

 teeth may be observed with the aid of a microscope. A skin is cast 

 off by successive contortions, wriggles, or squirms (if I may use a 



