410 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



split tuts out a long shield-shaped piece in the lower side of the 

 pupal shell, which drops down and allows the prisoner, already 

 become a moth, to emerge as far as the narrow limits of the cocoon 

 will permit. Some caterpillars have the foresight to leave a partly 

 open door at the end of the cocoon for the convenience of the moth, 

 but the webworm does not concern itself about any such provision for 

 its future. Yet the moth escapes. Cocoons from which the moths 

 have emerged have a round hole at one end with the edges flaring 

 outward. It is presumed that the moth exudes a liquid from its 

 mouth that softens the wall of the cocoon sufficiently for it to push 

 through. The crumpled wings then expand, the feeble legs gain 

 strength and, when night comes, the moth flies back to freedom in 



the trees. 



But what a transformation the creature has undergone since its 

 larval days. The moth is the perfect insect and is like its parents, 

 but the caterpillar has departed far from its ancestral line. By 

 letting its appetite get away with it, it degenerated into a worm, and 

 nature had to shut it up in the pupal shell to reform it and make 

 it over again into a moth. The cocoons are often to be found 

 amidst damp, dark, moldy surroundings under rubbish on the ground, 

 and the gentle snow-white moths, with their large, soft black eyes, 

 emerging from such incongruous environments seem to signify that 

 the caterpillar' sins have been fully expiated. The purified creature 

 will henceforth eat no more. Perhaps a dewdrop will slake its 

 thirst, but solid food will never pass its lips, nor will it be tempted, 

 for it has no jaws (fig. 11) and probably no appetite. Its body 

 contains a supply of predigested nourishment stored up by the 

 caterpillar sufficient for the rest of its life. The business of the 

 moth is to produce the eggs that will generate the succeeding brood of 

 caterpillars. 



The moths from the spring generation of caterpillars lay their eggs 

 during the latter part of July and the first half of August, placing 

 them on the undersides of leaves as did their parents in the 

 spring before them. A second brood of caterpillars issues in a 

 shorter length of time than did those produced by the spring eggs, 

 because the weather is now warmer and hastens the incubation, 7 

 to 10 days being usually sufficient at this season, whereas in the spring 

 eggs remained unhatched for as long as 15 days. The young web- 

 worms proceed at once with the construction of another set of tents 

 which are finished by late summer or by early fall. Then the full- 

 grown caterpillars are again to be seen wandering at large, till they 

 in turn spin their cocoons and change to pupae. The fall pupae, 

 however, are destined to remain within the cocoons until the follow- 

 ing spring, for the moths that emerge from them are those that will 

 start the webworm life all over again next year. 



