24 ILLINOIS BIOLOGICAL MONOGRAPHS [24 



ments and other larvae as they are reached. While it is not feasible to 

 discuss their homology in detail in this place, some of the evidence sup- 

 porting the view expressed is usually given, except where the corre- 

 spondence is entirely obvious. Section V then takes up each seta in turn, 

 follows it through its principal migrations and modifications, and 

 briefly summarizes the evidence for each case of homotypy. 



SUBORDER JUGATAE 



Of the suborder Jugatae the writer has studied in detail but one 

 genus, Hepialus, and the description will be limited to it. The setae of 

 larval Micropterygidae have been so reduced by leaf-mining habits that 

 conclusions can not be based on them. Hepialus, on the other hand, 

 seems still to be generalized and, as its wings gave Comstock the clew 

 to the ancestral venation, so its chaetotaxy has suggested the generalized 

 setal plan. 



Had Dyar studied the prothorax of the larvae of this genus as care- 

 fully as he did the other segments the following description would not be 

 necessary. As it is, the writer is compelled to rely on his figure of the 

 first stage; for up to the present time no newly hatched larvae have 

 been available for study. As this first stage is essential in the determi- 

 nation of homology, my results are based on the assumption that his 

 figures are correct. Descriptions of the later stages in this paper were 

 made from Hepialus humuli, verified by comparison with H. hectus and 

 H. lupulinus, two or more individuals of each species being studied. 



First Instar 



[Figs. 2, 3, 4] 



The prothorax of the newly hatched larva (Fig. 2) bears six setae 

 above the spiracle, two in front of it, two between it and the leg, and one 

 in front of the leg. No ventral setae are indicated. Those above the 

 spiracle are in two transverse rows of three setae each, those in the caudal 

 row being much closer together and farther ventrad than those of the 

 cephalic row. As shown on the figures, I have named those on the ceph- 

 alic row, alpha, gamma, and epsilon, and the caudal group, beta, delta, 

 and rho, beginning in each case near the dorsomeson. In front of the 

 spiracle, kappa and eta represent the Kappa group, and between the 

 spiracle and the leg the two setae, pi and mi, form the Pi group. The 

 seta in front of the leg is tan. 



The mesothorax and metathorax (Fig. 3) are practically identical 

 in their arrangement. As there is no spiracle, let us describe the setae 

 as above and below kappa, the single seta at the level of the prothoracic 



