PLATE XXXI. 



Figs. 1 and 4. Buenoa margaritacea, Bueno. Left and right view of the male genital 

 segment indicates the marked difference in the shape of the claspers. All the material 

 in this genus examined shows a similar asymmetry. The bulb here figured was taken 

 from a specimen identified by Mr. Bueno. L. C. = left clasper. R. C. = right clasper. 



Fig. 2. Buenocb elegans (Fieb). The genital bulb of this species differs from its 

 larger relative figured as above by the slight constriction as shown in the lateral profile 

 of the lower margin. The left clasper has a larger basal lobe than the Buenoa mar- 

 garitacea Bueno. The drawing is partly free hand, and the view is from the left side. 

 The specimen from which this drawing was made was determined by Mr. Bueno. C. = 

 clasper (left). 



Fig. 3. Plea striola (Fieb.). This tiny back swimmer has a genital segment somewhat 

 like its larger relatives. The drawing is made from the left side and shows the muscular 

 base of the penis. The claspers are curved, the right one is slightly more slender and 

 longer than the left — 'just a suggestion of asymmetry. This drawing is made from ma- 

 terial taken in New York. A study of Kansas material shows a slight difference. Bueno 

 has stated that he believes there is more than one species in the United States, and a 

 careful study of the material of the country may prove his contention. The material in 

 the Snow collections bears Bueno's label. C. := clasper (left). 



Fig. 5. Xotonecta — sp? Tlie male genital bulb from a specimen that came to me 

 among some Corixids. It lacks collector and locality label so it is not possible to say 

 from whence it came. D. C. = dorsal collar. L. C. = left clasper. 



Fig. 6. Notonecta indica Linn. The clasper is entire and the caudal margin of the 

 capsule has not the same shape as that of N. variabilis. The clasper of N. glauca re- 

 sembles it somewhat, but the capsule is very different in shape. 



Fig. 7. Notonecta irrorata Uhl. The genital bulb of the male of this species is very 

 different from the others in possessing a conspicuous fingerlike process on the ventral side. 

 This is usually lighter in color than the rest of the bulb. Material examined from Ithaca, 

 New York, and Wellington, Ohio. 



Fig. 8. Notonecta sp. In this species the clasper is broad and massive and very 

 shallowly bifurcate. From a study of some specimens collected by Chambliss at Knoxville, 

 Tenn. These bugs in size and general appearance resemble N. indica. The scutellum lacks 

 the lighter margin, however. 



Fig. 9. Notonecta insulata (Kirby). Genital bulb from a male specimen taken in 

 California. Note the singular shape of the capsule along its ventral line. In profile it 

 makes almost a right angle. Material from California and New York examined. 



Fig. 10. Notonecta undulata (Say). Genital bulb a little stouter than the majority of 

 the others. The claspers strongly bifurcate, the caudal branch thick and blunt, the other 

 long, curved somewhat mesally at tip. Material examined from Kansas, Missouri, and 

 New York state. 



Fig. 11. Notonecta variabilis (Fieb.). Genital bulb from a male specimen in the Snow 

 collections at Kansas University bearing label of identification by Mr. J. R. de la Torre 

 Bueno (specimen from Staten Island). Material also examined from Ithaca, N. Y. The 

 rather slender clasper is bifurcate at tip ; the caudal branch more slender than the other. 

 The quite evenly rounded caudal margin of the capsule is also different from those nearest 

 it in appearance. The ventral keel of the capsule is present and differs in shape from that 

 of N. undulata. 



Fig. 12. Notonecta glauca. The genital bulb or capsule from a male specimen given 

 to me by Mr. J. R. de la Torre Bueno and bearing the locality label of Milano, Italy. 

 The direction of the dorsal collar (D. C.) is directed backward somewhat instead of up- 

 wards as in most specimens. The clasper is entire and the bulb lacks the ventral keel 

 possessed by N. indica, N. undulata and N. variabilis. The specimen was slightly damaged 

 and the delineation may not be exactly true. 



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