271] NOCTUID LARVAE— RIPLEY 29 



and Dampf in spite of their widespread occurrence in the order. The latter 

 figures them in the psychid, Eumeta, and the former in an unnamed noctuid 

 and in Incurvaria, where he labels them xa, xb, xc and xd. They have been 

 found by the author in nearly all noctuids examined and in the cossid 

 Zeuzera pyrina, where they are extremely minute. They are undoubtedly 

 primary, since they have been seen in the first instar of Cirphis unipunda 

 and of Phytometra brassicae. They most probably occur in all newly 

 hatched noctuid larvae, if not in those of all caterpillars. Their extreme 

 minuteness renders necessary a most careful search in order to locate them. 

 The ventral two, xc and xd, occur only on the mesothorax and metathorax 

 and apparently correspond to the subprimary gamma of Fracker, which, he 

 states, is primary on the prothorax. These setae perhaps represent a vesti- 

 geal verruca, the two together being homologous with one seta. In 

 Hepialus there are three small setae in this region instead of two, as Fracker 

 has shown. On the Noctuidae either one or both of the minute setae xa 

 and xb are present on all segments but the prothorax and the anal one. 

 Xa of the mesothorax has apparently migrated onto the caudal margin of 

 the prothorax. These two setae appear to represent but one primary one 

 just as a verruca corresponds to a single seta. 



The homodynamy of these four minute setae cannot be definitely 

 established without involving an extensive study of the setal patterns 

 of caterpillars in general, especially of the first instars. Their position, 

 nevertheless, suggests homodynamy between alpha of the prothorax and 

 xa plus xb of the following segments and between gamma of the former 

 and xc plus xd of the mesothorax and metathorax. If this be true, beta and 

 delta of the prothorax correspond respectively to alpha and beta of the 

 following segments, other homodynamies remaining unchanged. This 

 interpretation reveals a much closer similarity between the prothorax and 

 other segments than that of Fracker, in which the minute setae were dis- 

 regarded. It seems preferable, however, to retain the names of Forbes for 

 these setae pending more extensive study on this question. 



Variations in the setal pattern of the prothorax are clearly discernible 

 and generally fairly constant for genera but they are so slight and grade so 

 continuously that very little taxonomic aid is afforded by them. The 

 location of beta varies longitudinally to some extent, ranging from a 

 position on the transverse line of beta to one distinctly caudad of it. Rho 

 exhibits some transverse variation, being either equidistant from delta and 

 the spiracle, as in Polia medilata, or much nearer to the latter, as in Nephe- 

 lodes emmedonia. The situation of epsilon with reference to gamma and 

 to the spiracle offers the best character in setal position on the prothorax. 

 In the Acronyctinae, CucuUinae, and Hadeninae epsilon may be distinctly 

 nearer to either according to the genus. It is apparently always nearer to 

 the spiracle on the CatocaHnae and Phytometrinae, but ranges in the 



