1918] Morphology of Genitalia of Insects 135 



and somite eight, as has already been mentioned in another 

 connection. This is well illustrated by the female saw-flies and 

 Vespa (Plate XVII, Figs. 10 and 14) as well as by the generahzed 

 genus Lepisma in the male. The size of these appendages varies 

 with their function. In the Orthoptera they attain a good size 

 in all the forms studied, in both the male and the female, being 

 more prominent in the latter. They are often apparently small 

 tactile organs in the male when Appendages II and III are 

 highly specialized, as in the case of Benacus, Euschistus and 

 Anasa, Appendage I being even less conspicuous in the females 

 of the two last mentioned genera, and somewhat smaller than 

 in the male. In those groups having a complete metamorphosis 

 it is either rudimentary, as in the female Hepialus; absent alto- 

 gether as is most often the case in both the male and female of 

 the Coleoptera and in female Lepidoptera other than Hepialus; 

 or specialized as so-called claspers in most male Neuroptera, 

 Mecoptera, Trichoptera, and Lepidoptera other than Hepialus. 

 In the Diptera, it is rudimentary in the female Tabanus; of 

 good size in both the male and female Tipula, and in the male 

 Tabanus; and small in both sexes in Calliphora. 



7. Appendages II and III. — These appendages are prom- 

 inent in those females which have their genitalia specialized to 

 dig holes in which to lay their eggs, to sting, or to perform some 

 other accessory function. Examples of these are common 

 among the Orthoptera and Hymenoptera (Plates V, VI, VII 

 and XVII). Even here Appendage II, referred to above as the 

 "mesal" appendage of certain authors, is small or rudimentary, 

 and it is found to be more often absent altogether in the female 

 than in the male. In the male these appendages are most 

 specialized in connection with the intromittent organ, and 

 Appendage II is more often present in the male than in the 

 female. The best examples of this modification are seen in the 

 Hemiptera and Coleoptera (Plates VIII, IX, X, XI and XII). 

 Similar organs, much smaller in size, are also found in Corixa, 

 Notonecta, Corydalis, Dolerus, and Vespa, made up, in all these 

 cases of Appendage II, as well as III. 



8. Appendage IV. — Appendages included under this head 

 are most often called the cerci. These are more dorsal in posi- 

 tion than the others, and seem in many cases in adults, espe- 

 cially in the Orthoptera, to be as well attached to somite ten as 



