31] LEPIDOPTEROUS LARVAE — FRACKER 31 



to be rho. This leaves only three setae, which are certainly kappa, pi, 

 and sigma. All of these conclusions are based on series of intermediate 

 stages. 



Segment 10 bears only one seta less than in Hepialus but the 

 homology is not clear. 



The mature Feltia (Figs. 21 to 24, 31, 32) shows certain modifica- 

 tions of the chaetotaxy of the first stage. The arrival of theta and 

 gamma on the mesothorax and metathorax, the first caudodorsad of 

 kappa, the other near the cephalic border of the segment, are the only 

 changes duplicated on Hepialus. On all the thoracic segments eta ap- 

 pears ventrad of kappa. As it was not present at all on the last two 

 segments of Jugatae, the condition here shows that since its establish- 

 ment on the abdomen it has arisen on the thorax, where, under Weis- 

 mann 's law, it has not yet reached the first instar. Finally mu, the most 

 recent arrival of all the subprimaries, appears caudoventrad of eta on 

 the first eight abdominal segments. 



A significant change in position also occurs after the first molt, 

 Epsilon, located below alpha and gamma in the cephalic subdorsal row 

 of the prothorax in the first stage, now appears close to rho above the 

 spiracle. This migration distinguishes the Bombycoidea from the Micro- 

 lepidoptera, for in the latter group epsilon remains near the cephalic 

 border of the prothoracic shield. 



Microlepidoptera 



Altho the differences between the Noctuidae and the Microlepidop- 

 tera are not great, the latter are more generalized in some important 

 particulars. These are best shown by Pseudanaphora (Figs. 7, 8, 15, 

 16), a member of one of the most generalized families of the order. On 

 the prothorax theta is present, so that all three setae of the Kappa group 

 are accounted for, just as in Hepialus. On the abdomen, kappa and 

 eta are at the same level but still distant, altho in all the higher micros 

 these setae are close together below the spiracle. As in the noctuid 

 abdomen, mu is present and theta is wanting. Segment 9 shows nearly 

 as many setae as in Hepialus, there being only two important differences ; 

 the absence of tau and theta, and the presence of mu caudoventrad of 

 eta as on the other segments. 



Other Groups 



The high specialization of the armature of saturnian, sphingid, and 

 butterfly larvae lessens their value as evidence on the homology of the 

 setae. The first instar is usually similar to that of the Noctuidae. Only 

 one serious problem is presented, viz., the origin of the scolus Kappa 



