Page:Insects - Their Ways and Means of Living.djvu/340



provender, enjoying for a while a new lire free from the domestic routine that bas bound them since the days of their infancy. But even their liberty has an ulterior pur- pose: the time is now approaching when their lives as caterpillars must end and the creatures must go through the mysteries of transformation, which, if successfully accomplished, will convert them into winged moths. I't would clearly be most unwise for the caterpillars of a colony to undergo the period of their metamorphosis huddled in the remains of the tent, where some untoward event might bring destruction to them all. Nature has, therefore, implanted in the tent caterpillar a migratory t,rge, which now becomes active and leads the members of

'I;. |çI. The cocoon of atent cater- pillar. (Natural size)

a family to scatter far and wide. About a week is allowed for the dispersal, and then, as each wan- derer feels within the first warnings of ap- proaching dissolution, it selects a suitable place for inclosing itself in a COCO011.

I t is diflàcult to find many cocoons in the neighborhood where large numbers of caterpillars have dispersed, but such as may be recovered will be round among blades of grass, under ledges of (ences, or in sheds and barns where they are not disturbed. The cocoon is a slender oval or a]most spindle-shaped object, the larger ones being about an inch long and hall an inch in width at the middle I Plate 4 E Fig. l çl). The structureis spun ofwhit¢ silk thread, but its waÏls are stiffened and colored by a yellow- ish substance infiltrated like starch through the meshes of the fabric. In building the cocoon the caterpillar first spins a loose network of threads at the place selected, and then, using this for a support, weaves about itself the walls of the final

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