1918] Morphology of Genitalia of Insects 131 



Table of Sclerites and Appendages. 



somites appendages 



Dolenis unicolor 7, 8, 9, 10, 11 L II, HI, IV. 



Female t+ t+ t+ t+ t— + + + + 



s+ s+ s+ s+ s — 



Male t+ t+ t+ t+ t— + + +,— 



s+ s+ s+ s+ s— 

 Vespa maculata 



Female t+ t+ t+ t+ t— + + + — 



s+ s+ s+ s+ s — 



Male t+ t+ t+ t+ t— + + + — 



s+ s+ s+ s+ s+ 



III. SUMMARY. 



Comparisons between certain of the somites of the different 

 orders investigated, as well as between some of the appendages 

 studied, may well be taken up as a summary of the above dis- 

 cussions and tables. The homology of the sclerites of the 

 species studied, as well as that of the appendages, has been 

 fully and clearly indicated in the labeUng of the figures. 



1. Somite Eight. — This somite, as has already been noted, 

 contains, typically, the terminal pair of spiracles. Except in 

 those species which have well-rounded contours, or are pointed, 

 at the caudal end of the abdomen, this somite approaches very 

 nearly the one figured in the so-called primitive type (Plate IV, 

 Fig. 1). It is simple in outline; broad and blunt in shape; 

 about one-third as long as wide ; tapering only very sHghtly, if 

 at all, and with a tergum and sternum almost equal in size, con- 

 nected laterally by an appreciable conjunctiva; in the Thysa- 

 nura, Orthoptera, Hemiptera, and in the generalized orders 

 studied having a complete metamorphosis, such as the Neurop- 

 tera, Mecoptera, and Trichoptera. In the Coleoptera and 

 Lepidoptera it is retracted ; more or less membranous ; long in 

 proportion to its width; and, in the Lepidoptera, except for the 

 possible case of Hepialus, it lacks its respective spiracle. It is 

 also small in the higher families of the Diptera, but its extreme 

 speciahzation occurs in the female Hymenoptera where the 

 sternum consists of two small, sub-triangular sclerites to which 

 is attached its: respective pair of appendages, I, saws or sting as 

 the case may be. (Plate XVII, Figs. 10 and 14). 



2. Somite Nine. — This somite is more speciahzed than the 

 eighth and markedly shorter in proportion to its width even in 

 the Thysanura and Orthoptera. In these generaHzed orders of 



