28 ILLINOIS BIOLOGICAL MONOGRAPHS [270 



names descriptive of the location of the setae to which they refer. We fail 

 to understand why a difference of opinion as to homodynamy should render 

 advisable the addition of yet a new system to our already superfluous 

 supply. The fact, moreover, that particular setae may be located in widely 

 different positions according to the segment and to the species opens to 

 objection all names of setae descriptive of position. Schierbeek would 

 change the names of the setae in instances of this sort, maintaining a 

 nomenclature should provide a simple means of describing larvae, rather 

 than of indicating questionable homologies. Inasmuch as the general 

 progress of all morphology and of taxonomy, which should always be based 

 on morphology, depends largely upon the correct homologizing of struc- 

 tures, we can by no means accept this view, even in cases where the homolo- 

 gies indicated by the nomenclature are doubtful. The shortness of the 

 names of Greek letters compared to the very long ones proposed by Schier- 

 beek also favors the use of the former. Furthermore, because of the great 

 utilitarian value of Tracker's tables, this system will probably come into 

 more general use than any other. For these reasons it will be used in this 

 paper so far as possible. Schierbeek's plan of naming the types of setal 

 arrangement of numerals seems very commendable. No occasion arises, 

 however, for using it in this work. 



Except for the marked differences in the development of verrucae 

 exhibited solely within a few genera of the Acronyctinae, the setae of 

 noctuid larvae offer comparatively little variation. Certain minor varia- 

 tions in their number and situation, however, are of great phylogenetic 

 significance because of their fundamental nature. Figures 47, 48, and 49, 

 showing the setal position in Cirpbis unipunda, represent the t>'pical con- 

 dition for the family. The naming of the setae in these figures differs 

 slightly from Fracker's labeling of those of Feltia gladiaria. As clearly 

 shown, both by his own figures and by those of the author, his tau on 

 segments 7 and 8 should be omega. The setae on the anal larvapod are not 

 named in his figure of Feltia, where their number and position is quite 

 different from that in Hepialus. Consequently the letters used to designate 

 these setae may not correspond to those in Fracker's figure of Hepialus, 

 which, as he states, do not necessarily indicate homodynamy with setae 

 bearing the same names on other segments. The seta on the anal segment 

 of Feltia which apparently corresponds to his theta on Hepialus is primary 

 in the former, since it occurs in the first instar of this species. Consequently 

 it should not be called theta, which is subprimary according to Fracker. 

 It is referred to as kappa in this paper. 



Certain minute setae are omitted from Fracker's figure of Feltia. 

 Omega should be present on segments 1 and 9 and the minute setae labeled 

 X in our figures were either generally overlooked by him or considered as 

 secondary. These seem to have escaped the notice of all workers but Forbes 



