57] LEPIDOPTEROUS LARVAE — FR ACKER 57 



jj. Prothorax and abdominal segment 8 with spira- 

 cles no larger than those of other segments. 



THYATIRIDAE 

 hit. Number of pairs of ventral prolegs reduced, cephalic 

 three pairs rudimentary or wanting. 



GEOMETRIDAE 

 ee. Setae of body secondary, always numerous at least on pro- 

 legs; anal pair and four ventral pairs of prolegs always 

 present, 

 f. Secondary setae very irregular in length, very long setae 

 mixed with others a tenth as long; neither distinct ver- 

 rucae nor scoli ever present; body often bearing latero- 

 ventral, blunt, fleshy protuberances, 

 g. Labrum deeply uotched, notch acute, either reaching 

 over two-thirds the length of the labrum or continued 

 as a groove which reaches clypeus ; several mediodorsal 

 pencils of setae often present. EUPTEROTIDAE 



gg. Labrum obtusely notched; notch variable but never 

 reaching two-thirds distance to base of labrum, never 

 continued as a groove which reaches clypeus. 



LASIOCAMPIDAE 

 ff. Secondary setae usually short and uniform in length ; 

 when long and irregular either distinct verrucae or scoli 

 are present. 

 g. Body usually armed with a mediodorsal horn, scar, sco- 

 lus, or pair of scoli on segment 8 ; if not, head produced 

 into a high conical point ; scoli never present on head 

 nor on dorsomeson of segments 1 to 7 ; head smooth ; 

 crochets usually only biordinal. 

 h. Body sphingiform, never bearing even rudimentary 

 scoli or secondary setae above level of prolegs. 

 i. Segments divided into six to eight annulets; prolegs 

 not widely separated. SPHINGIDAE 



ii. Segments not divided into annulets ; prolegs widely 

 separated. BOMBYCIDAE 



hh. Body not sphingiform, always bearing at least rudi- 

 mentary scoli. SATURNIOIDEA 

 gg. Body usually not armed with a mediodorsal horn, scar, 

 scolus or pair of scoli on segment 8; when so armed, 

 either segments 4 to 7 also bear unpaired mediodorsal 

 scoli or the head is conspicuously bigibbous above, 



