92 ILLINOIS BIOLOGICAL MONOGRAPHS [92 



aa. Front extending less than two-thirds of the distance to vertical tri- 

 angle* J adfroutals not reaching vertical triangle ; ocelli subequal in 

 size, 

 b. Rho on eighth abdominal segment directly dorsad of spiracle. 



Hymenia 

 bb. Rho on eighth abdominal segment cephalodorsad of top of spiracle, 

 c. Second ocellus about half way between first and third; seta vii 

 usually closest to second ocellus; penellipse more than a semi- 

 circle, 

 d. Front with sides straight or concave, 



e. Alpha and rho on ninth abdominal segment in a horizontal 

 line ; head not depressed ; labrum with a rounded emargi- 

 nation. Pachyzancla 



ee. Alpha and rho on ninth abdominal segment not in a hori- 

 zontal line, except in some species in which the labrum has 

 an acute notch, 

 f . Head very much depressed ; labrum with an acute notch. 



Desmia 

 if. Head not depressed ; labrum usually not with an acute 

 notch, 

 g. Pinacula heavily chitinized, black. Pyrausta 



gg. Pinacula slightly chitinized, pale. Phlyctaenia 



dd. Front with sides rather convex throughout their entire length ; 

 seta vii closest to third ocellus, 

 e. Adfroutals conspicuously widened above the front. Sylepta 

 ee. Adfroutals not widened above the front. Terastia 



ec. Second ocellus much closer to first than to third ; seta vii closest 

 to third ocellus ; penellipse less than a semicircle, 

 d. Setae alpha of first abdominal segment more than twice as far 

 apart as each is from beta ; body bearing subdorsal longitu- 

 dinal stripes or dotted areas ; subdorsal pinacula heavily 

 chitinized. Evergestis 



dd. Setae alpha of first abdominal segment not more than one 

 and a half times as far apart as each is from beta, 

 e. Alpha directly dorsad of rho on eighth abdominal segment, 

 f. Labrum very broad and short, shallowly but acutely 

 emarginate ; head spotted. DicJiogama 



ff. Labrum normal, with a rounded emargination ; head uni- 

 colorous. 

 g. Thoracic legs and abdominal prolegs short and often 

 stout. 



*Except sometimes in Evergestis which may fall in "a". 



