2751 NOCTUID LARVAE— RIPLEY 33 



The spiracle has also migrated in a transverse direction, as indicated by 

 its position with reference to the surrounding setae. In general it is further 

 ventrad on segment 1 and further dorsad on segment 8 than on segments 2 

 to 7 inclusive. Sometimes segments 7 and 8 present the same condition, 

 as in Scolecocampa liburna, which is to be regarded as a specialization, since 

 segment 7 as well as segment 8 has departed from the primitive arrange- 

 ment. In Sidemia segment 8 does not differ in the transverse position of the 

 spiracle with reference to epsilon from segments 2 to 7, as it does in the 

 other genera examined. This may be reasonably considered as a generaliza- 

 tion. 



From this consideration of the position of the spiracle it appears that 

 segments 2 to 6 inclusive present the primitive condition, the spiracle 

 having migrated cephalad on segments 1 and 7 and either cephalad or 

 caudad on segment 8 depending on the group. It has, moreover, shifted 

 ventrad on segment 1 and dorsad on segment 8, remaining usually in the 

 same transverse position on segment 7 as on segments 2 to 6. 



The taxonomic value of the transverse variation of kappa in cater- 

 pillars was early demonstrated by Dyar. Altho the situation of this seta 

 offers no conspicuous differences in this family, it varies sufficiently to 

 provide some generic characters. It is usually much further ventrad of the 

 spiracle on segment 7 than on other segments. Achalodes zeae again affords 

 an exception, having kappa further ventrad on segment 8 than on segment 

 7, the reverse usually being true. Differences in the location of eta and mu 

 afford generic characters, especially on segment 7, where they vary both 

 transversely and longitudinally. The transverse position of omega relative 

 to pi and sigma varies considerably throughout the family, seemingly 

 according to the genus. The very minute size of omega, however, unfor- 

 tunately precludes the use of this character in a table. 



On segment 8 beta is tj-pically much further dorsad than on the seg- 

 ments cephalad of it, presenting a specialized setal arrangement. The 

 longitudinal line through alpha may pass considerably above beta or a 

 little below it, the latter more specialized condition being less frequently 

 encountered. This character promises to be useful in the separation of 

 genera and of larger groups. Pi varies transversely to some extent on 

 segment 8 relative to mu and sigma, affording generic characters. 



With the exception of the anal one, segment 9 may reasonably be 

 regarded as the most specialized segment with respect to setal pattern. 

 Here the migration dorsad of beta has proceeded much further than on 

 segment 8. The transverse location of alpha relative to beta and rho varies 

 according to the group, altho presenting considerable individual variation 

 in some species. Rho may be nearer either to alpha or to beta depending 

 on the genus. The transverse line through kappa may pass either caudad or 

 cephalad of pi, both of these setae varying somewhat in their situation 



