112 ILLINOIS BIOLOGICAL MONOGRAPHS [112 



difference either of kind or of degree. On the other hand the half-dozen 

 exceptions include species which resemble arctians, lasiocampids, noto- 

 dontids, eupterotids, etc., and which have been distributed by some 

 authors into a variety of families. Naturally it is the latter forms 

 which are most difficult to handle in a synopsis of the entire order but 

 which are easy to separate from each other. 



It is not a part of the plan of this paper to enter the subject of the 

 classification of Noctuidae. The range must, however, be considered. 

 Many of the larvae are of such structure that they will not trace to the 

 correct family in any tables hitherto published. It is clear that differ- 

 ent characters must be used in identification according as the setae are 

 primary or secondary or developed into tufts, the crochets biordinal 

 or uniordinal, and the body cylindrical or with prominent humps. We 

 must then divide the family into four groups, of which the first will 

 include nearly all the genera, most of the larvae being of the "cut- 

 worm" type, and the others will be confined to the genera Demas, Pan- 

 thea, Acronycta, Harrisimemna, Agriopodes, Polygrammate, and a few 

 others of minor importance. Larvae of Acronycta will be found in all 

 groups except the first, but species of the other genera mentioned are 

 few in number and individuals rare. These ''groups" are purely for 

 convenience and do not constitute a "natural" arrangement. 



Group 1. Larvae with primary setae only; prothorax with beta 

 above level of alpha, epsUon associated with rho between delta and 

 spiracle, Kappa and Pi groups each bisetose; mesothorax with alpha 

 associated with beta, epsilon with rho, and kappa with eta, theta sepa- 

 rate. Pi group unisetose ; metathorax similar. Abdominal segments 1 

 to 6 and 8 with alpha above level of beta, rho above level of spiracle; 

 epsilon, when present, smaller, and located cephalodorsad of spiracle, 

 kappa and eta widely separated, mu present. Pi group consisting of 

 three setae on most segments; sigma present; no other setae present 

 except sometimes a few members of the Tau group and sometimes 

 gamma ; segment 7 similar, except that kappa is always much lower and 

 closer to eta; segment 9 with alpha, beta, and rho forming a triangle, 

 kappa, eta, mu, pi, and sigma present. Prolegs present on segments 5, 

 6, and 10, at least, and usually on segments 3 and 4; crochets arranged 

 in a mesoseries, uniordinal except in some Plusiinae and others, in which 

 the crochets are biordinal. This group contains the vast majority of 

 genera but none of the species of Acronycta. (Figs. 17-24, 29-32.) 



Group 2. Larvae with well developed verrucae (Figs. 65, 66), 

 Arrangement of tufts similar to that in Arctiidae except that kappa is 

 lower on segment 7 than on segments 6 and 8 (scarcely lower in Cha- 

 radra) ; in one-fourth of the species kappa is reduced to one or a few 

 setae and is easily overlooked. The crochets of the species of Acronycta 



