2511 NOCTUID LARVAE— RIPLEY 



LARVAL MORPHOLOGY 



Noctuid larvae, with the exception of a few genera, are characterized 

 by their marked uniformity of structure. Of these the genus Acronycta 

 and its allies, whose larvae resemble those of the arctiids, with their charac- 

 teristic tufts of setae, has been treated by Dyar to the number of about 

 fifty species. The larvae of certain other genera look like those of the 

 Geometridae, lacking one or two pairs of larvapods. For the greater part, 

 however, noctuid larvae are uniform with regard to most of the characters 

 used by Fracker in his key to lepidopterous larvae. The poskion of body- 

 setae, for instance, the taxonomic value of which was early pointed out by 

 Dyar and which plays an important role in Fracker's work, is very nearly 

 uniform thruout the family. The same may be said of the arrangement 

 of the crochets. Certain head-structures, however, first emphasized by 

 Forbes, are variable within the Noctuidae. Crumb, in his key to cut- 

 worms injurious to tobacco, used various types of skin-sculpture, the 

 microscopic structure of the cuticle of the body. The conspicuous varia- 

 tion in the number of larvapods has, of course, long been known. With the 

 exception of Dyar's monograph of Acronycta and its allies, and Crumb's 

 artificial key for the identification of fourteen species of tobacco cut-worms, 

 we have no works dealing with the classification of noctuid larvae. Fracker, 

 however, gives characters for separating the family from all others but the 

 Agaristidae. He divides it into four groups, all of which are listed in 

 different places in his table. The following morphological study has been 

 made to determine the taxonomic value of the structural variation which 

 this family exhibits in its larvae, as well as to provide the basis for a post- 

 embryological study of the group. 



FIXED PARTS OF THE HEAD 



Since the structure of the head (Figs. 1-17) of noctuid larvae does not 

 differ fundamentally from that typical of the entire order, the morphologi- 

 cal treatment which follows applies for the most part to lepidopterous 

 larvae in general. The epicranial suture assumes the form of an inverted Y 

 (Fig. 2) with the stem following the dorsal portion of the meson and the 

 two arms extending ventrolaterad on either side. Since the epicranial 

 stem represents the median line of dorsal closure in the embryo, the arms 

 being derived from the closure on either side of the so-called unpaired 

 appendage, the homology of this suture with that of the larvae of all other 

 orders is unquestionable. In nymphs or adults of the Orthoptera the 



