G. C. CRAMPTON 221 



more like those of the ^Mecoptera than they are, since there is 

 considerable evidence that the Mecoptera (with the Neuroptera) 

 are very like the ancestors of the Trichoptera. 



In most cases, the evidence afforded by a study of the genitalia 

 directly supports that drawn from other sources, which served 

 as the basis for the grouping of insects into superorders given 

 by us,'^ and in no instance would the character of the genitalia be 

 incompatible with such a grouping. On the other hand, the 

 nature of the genitalia of many insects offers no striking evidence 

 of relationship one way or the other, and one must depend upon 

 the study of other characters from as many different portions 

 of the body as possible, to determine the inter-relationships of 

 the orders of insects. Furthermore, insects are usually not 

 uniformly primitive or specialized in all parts of their bodies, 

 and an insect which is quite primitive in most respects may have 

 the genitalia more or less specialized, while an insect which is 

 otherwise fairly speciaHzed may preserve the genitalia in a con- 

 dition closely approximating the ancestral condition of the group 

 to which it belongs. Thus it is largely a matter of luck in finding 

 the right insect to illustrate the condition of genitalia which 

 one feels sure must be exhibited by some meml)er of the group, 

 from evidences of relationship to another group of insects in- 

 dicated by the general make-up of the body as a whole. Since 

 I have not as yet succeeded in finding the forms (which I feel 

 sure exist from a study of other features) connecting the Tri- 

 choptera with the Mecoptera and both of these with the Neurop- 

 tera, in the character of their genitalia, it is preferable to i)ostpone 

 further discussion of the evidence of relationship furnished by 

 the genitalia until the series is complete. I would make use 

 of this opportunity of requesting the privilege of examining the 

 genitalia of such Trichoptera as anyone may be willing to lend 

 for this purpose. 



^ Canad. Entomol., LIII, p. 114, 1921. 



TKANS. AM. ENT. SOC, XLVHI. 



