273] NOCTUID LARVAE— RIPLEY 31 



kappa, theta, and eta relative to one another also varies sufficiently to 

 provide some characters. Kappa may be equidistant from eta and theta 

 or very much nearer to eta. Most commonly it is slightly but distinctly 

 nearer to the latter, being especially close to theta in the Catocalinae, 

 Phytometrinae, and Hypeninae, a group of subfamilies which, as will be 

 shown later, conform as a unit to certain other very fundamental char- 

 acters. The angle made at kappa by the lines kappa-eta and kappa-theta 

 varies in size from 80 degrees to a very obtuse one according to the genus. 

 The most marked variation in setal position exhibited on the mesothorax 

 and metathorax is furnished by xc and xd. Although closely associated, 

 they vary not only relative to each other but also in transverse position 

 with reference to epsilon and rho, ranging from a point a little above rho to 

 one slightly below epsilon, the latter condition having been found only in 

 Achatodes zeae. Their minute size, however, would render impractical their 

 use in tables. The fact that much greater variation occurs in the setal 

 arrangement of these segments than in the prothorax would seem to sup- 

 port Fracker's contention that the condition in this respect is more primi- 

 tive in the latter. The setal pattern of the mesothorax and metathorax, 

 however, is on the whole very uniform. 



The arrangement of the setae of abdominal segments 1 and 2 differs 

 essentially from that of the other segments only in the region where larva- 

 pods are borne on the following segments. The setae which are normally 

 borne on the larvapods on segments 3, 4, 5, and 6 are present on this portion 

 of segments 1 and 2. The other setae of these two segments will be con- 

 sidered later in the general treatment of the abdominal setae which follows. 

 On segment 2 tau is apparently always well developed, but it has been found 

 on segment 1 only in the Catocallinae, Phytometrinae and Hypeninae. 

 Fracker figures it in the first abdominal segment of Feliia gladiaria, 

 although the author has failed to find it in an abundant supply of material 

 of this species. Omega, on the other hand, which is omitted from his 

 figure, is apparently always present in the family on this segment, although 

 very minute. The presence or absence of tau is the most fundamental 

 character discovered in our entire study of the morphology of the noctuid 

 larvae, making it possible apparently to separate two large groups of sub- 

 families on this basis. The position of omega varies considerably in a 

 transverse direction according to the genus, its minute size, however, 

 renders it inadvisable to use this variation in tables. Some difference in 

 longitudinal location is offered by sigma, which ranges from a position on 

 the transverse Hne through pi to one distinctly caudad of it. The Cato- 

 calinae apparently differ from other subfamilies in having the line nu-mu 

 longer than the line pi-mu on segments 1 and 2, the opposite condition 

 being distinctly present in all other larvae examined. On both these 

 segments, in those subfamilies where it occurs, tau varies both longi- 



