1918] Morphology of Genitalia of Insects 127 



e. Mecoptera. — Panorpa lugubris, the example chosen in this 

 case, seems at first glance to be a most specialized insect, par- 

 ticularly so far as genitaHa are concerned. This appearance is 

 found to be, with very little and superficial examination, 

 entirely misleading. The real situation at the posterior ends of 

 both the male and female Panorpa is that of a generalized form. 

 In the male there is a resemblance to the Lepidoptera in the 

 claspers, which are not, however, the only appendages present 

 as is usually the case in the larger group characterized by such 

 organs. 



Table of vSclerites and Appendages. 



SOMITES appendages 



Panorpa lugubris 7, 8, 9, 10, 11 I, II, HI, IV. 



Female t4- t+ t+ t+ t+ + _ -|- + 



s+ s+ s+ s-j- s-j- 



Male t+ t+ t+ t+ t— + — + + 



s+ s+ s+ s+ s+ 



/. Trichoptera. — The male caddis fly is characterized by an 

 apparent specialization, real indeed so far as function is con- 

 cerned but not fundamentally affecting the relative arrangement 

 of parts. The specialization is in connection with the pro- 

 longation merely of the ejaculatory duct, and is formed of 

 Appendage II. 



Table of Sclerites and Appendages. 



g. Coleoptera. — The Coleoptera have long presented a great 

 problem to those investigators who wished to be able to make a 

 classification of that group based on genitalia. So far as this 

 paper is concerned they may still present almost unsurmount- 

 able difficulties. However, there is very Httle doubt that ten 

 segments and even traces of eleven are present in the beetles, 

 even if one must depend in large measure upon membrane only 

 and asymmetrically placed sclerites. With relaxation by 

 potash it is very evident that true somites eight, nine, and ten 

 are present, the sutures between them showing plainly by means 

 of evaginated folds or grooves. The eighth somite is always 

 indicated plainly by the position of the eighth spiracle, no 



