THE UNIVERSITY SCIENCE BULLETIN. 331 



the drawings on plate XXXI. In the genus Buenoa we find 

 the beginnings of asymmetrical development in that the right 

 and left claspers are unlike. (A faint suggestion of this is 

 to be found in Pelocoris and Plea.) See the drawings on 

 plate XXXI, figures 1, 2 and 4. 



In the families Gelastocoridse and Corixidae are found 

 marked asymmetry, not only of the genital capsule and its 

 parts, but of the abdominal segments themselves as well. The 

 claspers of Gelastocoris are profoundly unlike — the ventral one 

 (the right one) is large, stout, and equipped with short, blunt 

 pegs or processes ; the other one is small and not greatly modi- 

 fied in shape. See plate XXXII, figure 5, R. C. and L. C. The 

 Corixid capsule and its parts are more complicated and per- 

 plexing than the forms above mentioned, but have been used 

 by the writer with success as an aid to the separation of 

 difficult species. 



There are figured, herewith, the male genital segments of 

 nine species in the genus Notonecta* — two in Buenoa, one in 

 Plea, two species of Amhrysus, two Saldids, and two Gelas- 

 tocorids. The reading of the discussion which follows should 

 be accompanied by an examination of plates XXXI and 

 XXXII. 



* The figures of Not07iecta raleighi Bueno, Notonecta shootcri, Uhl., Notonerta vhleri 

 Kirk., Notonecta montezuma Kirk., and Notonecta Ivtea Mull, are not figured. Notonecta 

 lutea from British Columbia, identified as such by Bueno, has a genital bulb much like 

 N. irrorata. The ventral process is shorter and located farther cephalad. The fold of the 

 lobe in front of the clasper extends to the ventral margin. The.se two species, N. irrorata 

 and the so-called lutea, are quite related. The genital bulb of Notonecta shooteri re- 

 sembles figure five very closely, and the bulb of Notonecta raleighi is very like that of 

 Notonecta variabilis. 



