THE FALL WEBWORM SNODGRASS. 405 



occupants of a tent are stretched out motionless, some on the outside, 

 some within, evidently simply indulging in repose. 



Whatever may be the secret motive of the webworms' industry, it 

 does not appear to involve the idea of protection from enemies ; for, 

 whatever benefits the caterpillars may derive from their elaborate 

 architecture, immunity from attack by other creatures is not one of 

 them. Any bird that cares to eat hairy caterpillars could make a 

 good meal almost any time from the outside of the webs; but the 

 only birds known to eat webworms are cuckoos and screech owls, and 

 certainly these do not cause any great depletion of the webworm 

 population. Garden toads will gulp down the wooliest of caterpillars, 

 even if they choke, but they do not climb trees. The worst enemies 

 of insects are other insects, parasitic species that lay their eggs in 

 the bodies of their victims. The webworms' web offers little shelter 

 against parasites. Caterpillars on the outside are exposed to direct 

 attack; and parasites with long, sharp ovipositors do not hesitate to 

 enter the edifice where they stab right and left at the occupants so 

 conveniently suspended in its meshes. Praying mantids, assassin 

 bugs, and hunting spiders are included amongst the known pre- 

 daceous enemies of webworms, but their toll on the colonies is only 

 comparable with that of thugs and murderers in human communi- 

 ties. Insects in general hold their place in nature by force of 

 numbers. Just as plants survive a multitude of destructive forces 

 through a superabundance of seeds, so insects maintain themselves 

 against odds by producing each season sufficient of their kind to 

 gratify the appetites of all their enemies and still be sure of enough 

 to propagate their species. 



A few days after the webworms have shed their fourth skins they 

 molt again and enter into the sixth and last stage of their larval 

 lives. They have now become superb creatures an inch in length 

 (fig. 8, and pi. 2, C), but they appear much longer than this on 

 account of the great spread of the body hairs. Those on the tuber- 

 cles along the sides of the back make an elegant sweep outward and 

 upward, those on the sides curve downward, covering a width nearly 

 equal to the length of the body. The dark band on the back is of a 

 soft, rich velvety black, parted by a narrow, fragmentary median 

 line of white and bordered on each side by the row of prominent 

 black latero-dorsal tubercles. In general, the colors are deeper, the 

 hairs longer, grayer, and woollier than in any of the preceding 

 stages; but sometimes it is difficult to distinguish at a glance small, 

 pale individuals of Stage VI from large, dark ones of Stage V. Meas- 

 urements of the head, however, give constant differences between all 

 stages. The webworms in Stage VI have heads two-fifths wider 

 than those of stage V. 

 101257—23 27 



