A Classification of Lepidopterous Lat^vse. 



197 



also on the legless abdominal segments (viz., segments 1, 2, 7, 8, 

 and 9 of the abdomen) in the corresponding position. On the last 

 two segments (segments 9 and 10) the number of tubercles is always 

 less than the fundamental number, even in generalized larvae. This 

 is due to the fact that these segments have been partly aborted, 

 being without spiracles. The reduction of segment 9 has taken 

 place on the anterior portion, while segment 10 has lost the lateral 

 part.^ 



Phylogeny of the Tubercles. 



In comparing the larvae of other orders of insects with the Lepi- 

 doptera, we find but few which throw any light on the origin of the 

 present arrangement of the tubercles. The Phryganidae, the imagos 

 of which seem to suggest an affinity with the Lepidoptera, have 

 larvffi without any tubercles, and also without any abdominal feet. 

 They have, however, a dorsal shield on the mesothoracic segment, 

 as well as on the prothoracic segment, a fact which is very interest- 

 ing in connection with the structure of the Hepialidfe and Psychidse. 



In the larvse of the phytophagous Hymenoptera (Tenthredinidae) 

 we find well-developed setiferous tubercles, apparently in a more 

 generalized condition than in any Lepidoptera. They have the fol- 

 lowing arrangement (see Fig. 1): Above the spiracle nine tubercles 



Fig. 1. 



Fiff. 2. 



Fi6. 1. — Diagram of a segment of a species of Tenthredinidse (Hylotoma McLeayi). 

 Fig. 2. — A segment of Hejjialus lupiniiliis (from a drawing by Mrs. P. N. Knopf). 



in a square, three on each of the fundamental subsegments or annu- 

 lets. Below the spiracle is the substigmatal ridge, divided into two 

 oblique portions, each thickly covered with setiferous tubercles. 



We may homologize these with the Lepidoptera as follows: In 

 the Jugat£e (see Fig. 2) the three tubercles of the middle annulet 



1 In the generalized Pyralid Pantographa limata G. & R., tubercles i and iii 

 are lacking on segment 9, tubercles iv, v, and vi on segment 10. 



