406 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



Ant- 



F I0- s. — Full-grown webworm in Stage VI (natural length about 1 inch). 



While the sixth stage is marked by an intensification of the phys- 

 ical characters of all the other stages, it is characterized by new traits 



of temperament. A spirit of in- 

 dependence now asserts itself — 

 the caterpillars will be bound no 

 longer by the rules and regula- 

 tions that have restricted their 

 lives thus far. They will live 

 for a while with the smaller 

 members of the family who have 

 lagged behind in Stages V and 

 Q IV, but they will do no work 

 about the house or out of it. and 

 they will totally ignore that rule 

 of webworm etiquette which for- 

 bids the eating of the entire leaf. 

 Instead of beginning at the 



Fig. 0. — A three-quarter facial view of a . . , 



webworm caterpillar's head, showing the Center and Stripping the Surface 



strong, toothed jaws or mandibles (Md) nnfw „ r J t y |pv j,^ bp<r'm at the 



which enable the caterpillar to bite off OUtWaTO, tney no^ Deglll ai UM3 



pieces of the leaves. The jaws are edge and devour the whole thick- 



hinged to the sides of the head between n .i 



the broad upper lip or labrum (Lm) and neSS, eatmg away all the tlSSlie 



the thick under lip found by the united J down to the l ar „ er ve i ns 



maxillae (Mx) and labium (Lb). The . & 



last carries the spine-like spinneret (Spu) and mid rib. Perhaps SOITIO, did 



through which the caterpillar spins its • ot tt i l ■ ~ 1 :* :„ 



silk. On the sides of the head are the SO 111 Stage \ , bllt in general it IS 



group of simple eyes or ocelli (O) and bad form for anv bllt sixth Stage 



the short antennae (Ant). * ' . . . 



caterpillars to feed in this man- 

 ner. Toward their smaller brothers and sisters, who are still laboring 

 with their spinning and weaving, the big indolent fellows comport 



