29J LEPIDOPTEROUS LARVAE — FRACKER 29 



In the first place it should be noted that while it is possible to name 

 these structures, there is no great amount of evidence as to their true 

 homology. If we call those on the plate epsilon, beta, and rho, then the 

 one on the suranal lobes must be theta. This would indicate that the 

 tenth segment is very similar to the ninth and gives us a hint as to the 

 other setae. The one on the mesocephalic aspect of the proleg would 

 thus be tau, and the one in a mesocaudal position, sigma, while the four 

 on the lateral aspect would represent pi, nu, omega, and phi. Calling the 

 two setae behind the proleg kappa and eta, completes the series. 



These setae have been named not so much to express an opinion 

 regarding their homology as to show that only one set is present. There 

 is only one more seta (phi) on this segment than on any of the other 

 proleg-bearing ones and one (epsilon) is missing. We may consequently 

 conclude that the setae give no evidence for considering the anal segment 

 to be composed of more than one metamere either in its dorsal or ventral 

 portions. The proof is especially clear either that the suranal plate 

 does not represent a telson, or that if it does the dorsal half of segment 

 10 has been entirely suppressed. Those who have asserted that the 

 setae show that this segment consists of more than one somite have not 

 studied carefully the data on which their opinions were based. 



Conclusions from a Study of Jugatae 



Hepialus has been considered in detail because it is very close to the 

 typical form and represents an entire suborder, the Jugatae. There are 

 some primitive features about it which give us a clue to the homology 

 in other groups. This is especially true of the thoracic segments, whose 

 relation to the abdomen and to each other would be wholly in the dark 

 without this form. The prothorax shows the same essential type of 

 arrangement as the other segments. It has been a failure to study He- 

 pialus carefully that has caused Miiller, Dyar, Quail, and Forbes to omit 

 the prothorax in their w 7 ork on the setae and to consider its chaetotaxy 

 as of wholly different origin. 



SUBORDER PRENATAE 



The chaetotaxy of the larvae of this suborder has been described 

 in detail by Dyar, and he has also compared it with the setal plan of 

 the Jugatae. A brief consideration of those modifications of the plan 

 which might be confusing in a determination of homotypes is all that is 

 necessary here. 



Bombyeoidea 



The Noctuidae are considered first, not because they are the most 

 generalized but because the writer has studied no other larvae in the 



