86 



ENTOMOLOGICAL SOCIETY 



vj V 



the structural differences w r ere overlooked. It is evident that the 

 insect figured by me in the American Entomologist (Vol. I, 

 Fig. 106) and in the Ninth Report on the Insects of Missouri 



(Fig. 33) as Belostoma 

 grandis was really Bena 

 cus griseus, and the eggs 

 figured (Fig. 32) in con 

 nection with the former 

 species, as probably belong 

 ing to it, evidently belong- 

 to the latter, judging from 

 dissections recently made. 



In figures 4 and 5 the 

 differences in the femora 

 and tibiae between the two 

 genera are illustrated, as also 

 the genitalia of both sexes. 

 The femoral grooves of Be 

 lostoma seem to vary some 

 what in intensity with dif 

 ferent individuals, and more 

 over the two grooves in the 

 same individual vary some 

 what in width. An impor 

 tant feature in this species 

 not previously mentioned is the smooth cavity or pit on the 

 inner border of the coxa where it articulates with the femur, 

 as shown in figure 4, a. It is against this surface that the 

 tarsal claw impinges when the tibia is closed upon the femur. 

 With Benacus there is no sign of this articulating facet, the 

 inferior surface of the coxa remaining convex and roughened 

 as shown in figure 5. The outer and upper end of the 

 clypeus in Benacus is velvety and dark-colored. In the ma 

 jority of specimens of Belostoma this spot is lighter in color, 

 and only occasionally velvety in appearance. The genitalia 

 of the two forms, when a large series is examined, are very 

 close in structure, as shown in the figures. After examination, 

 however, of a large number of specimens, the distinctions indi 

 cated in the drawings 4, c and 5, e seem to be reasonably constant 

 in the male sex, while the differences shown between 4, c and 5, b 

 are largely caused by the protrusion of the central organ. The 

 figures represent a dorsal view, after the wings and the dorsal 

 plates of the abdomen have been removed, while the lines be 

 tween the appendages indicate the tip of the abdomen, and of 

 the lateral expansions, beneath. 



FIG. 5. BENACUS GRFSEUS : a, front leg; b, tip of 

 abdomen of female, dorsal view, the wings and 

 dorsal membrane removed ; c, do. of male. 



