220 GENITALIA OF MALE DIPTERA AND MECOPTERA 



Before leaving the subject of the genitaha of male insects, I 

 would call attention to the evidence of relationship indicated 

 by the genitalia of the different groups of insects, which serves 

 to strengthen the conclusions regarding the inter-relationships 

 of these groups reached through a comparison of other structures 

 of the body than the genitalia. The character of the "larval" 

 head and mouthparts, the nature of the cerci and terminal 

 filament, and other structures of the body indicate that the 

 ephemerids are among the most primitive of winged insects, and 

 the character of the genitalia would bear out this view, since the 

 parts of the male in certain ephemerids approximate the funda- 

 mental type extremely closely. 



The head and mouthparts of certain Hymenoptera and Me- 

 coptera indicate a very close relationship between the two groups, 

 and their larvae are similar in many respects, so that the marked 

 similarity in the genitalia affords additional evidence of a close 

 relationship between the two orders indicated by other structures 

 of the body. The Diptera resemble the Mecoptera more than 

 any other insects in the nature of their head and mouthparts, 

 thoracic structures, etc., and the remarkable similarity in the 

 genitalia of the two groups leaves no room for doubt that the 

 Mecoptera are among the nearest living representatives of the 

 types ancestral to the Diptera, although recent Mecoptera are 

 naturally not the ancestors of recent Diptera. 



The genitalia of the Lepidoptera are very like those of the 

 Trichoptera, thus bearing out the evidence of a very close re- 

 lationship between these two groups of insects indicated by 

 other structures of the body as well. The genitalia of certain 

 Lepidoptera not figured in the present paper, indicate an ap- 

 proach to the Hemiptera (Homoptera) in some resi>ects, thus 

 tending to bear out the marked resemblance in the venation of 

 the two groups of insects, but the Hemiptera are rather unique 

 in many respects, and their genitalia are not as similar to those 

 of the Mecoptera, as one might expect from the resemblance of 

 the hemiptcrous mouthparts (labium, etc.) to those of the 

 Mecoptera and their allies, although the genitalia of some 

 Hemiptera are rather suggestive of those of certain Diptera and 

 other insects derived from Mccoptera-like forebears. It is also 

 rather surprising that the genitalia of the Trichoptera are not 



