121] LEPIDOPTEROUS LARVAE — FRACKER 121 



basis is impossible. They are never absent in American species so far as 

 examined, but in the last stage of the European Aglia tau, only great 

 dorsal gibbosities remain to show that the recent form has descended 

 from saturnian ancestors. 



Beta on the first eight abdominal segments of members of this 

 superfamily is either represented by a single seta or is wanting. The 

 eighth segment of Ceratocampidae is an exception, for here there is a 

 pair of small scoli caudad of the large mediodorsal scolus alpha. 



The crochets are always biordinal and arranged in a mesoseries. 

 (Fig. 106). The anal prolegs are usually flattened laterocaudally and, 

 with the anal plate, form a triangular pyramid. 



Families of Saturnioidea : 



a. Ninth abdominal segment not bearing a scolus on the dorsomeson; 



scoli never profusely branched; mediodorsal scolus of segment 8, 



when present, never associated with a pair of smaller scoli latero- 



caudad of it (Fig. 108). SATURNIIDAE 



aa. Ninth abdominal segment bearing a scolus on the dorsomeson (Figs. 



109, 110, 111). 



b. Scoli alpha of mesothorax scarcely longer than abdominal scoli; 



latter often profusely branched ; anal plate smooth. 



HEMILEUCIDAE 

 bb. Scoli alpha of mesothorax at least twice as long as scoli of 

 abdominal segments 1 to 6; scoli never profusely branched; 

 anal plate bearing at least one pair of small chitinous pro- • y 

 cesses. CERATOCAMPIDAE ''MjuuryUd, 



Genera of Saturniidae: 



a. Eighth abdominal segment bearing a scolus on the dorsomeson. 

 b. Scoli alpha of mesothorax and metathorax subequal in size to or 

 smaller than other body scoli ; scolus Pi never present on abdom- 

 inal segments 1 and 2. 

 c. Scoli well developed and conspicuous, cylindrical, higher than 

 wide. Philosamia 



cc. Scoli reduced to small knobs not higher than wide. 



d. Labrum notched to about one-half its depth; secondary setae 



rare or absent on dorsum. Rothschildia 



dd. Labrum notched to three-fourths its depth; secondary setae 



common on dorsum. 



e. Abdominal segments 1 to 7 each bearing a transverse yellow 



intersegmental stripe; scoli Rho and Kappa not connected 



by a yellowish ridge ; spiracle much closer to scolus Kappa 



than to Rho. Tropea 



