o 



14 The Ohio Journal of Science [Vol. XVI, No. 



tube (an. t.) opens to the exterior. The ventral portion almost 

 completely encloses the ovipositor (ovp.) which is generally 

 a long, rather slender, heavily chitinized organ, hinged to the 

 caudal end of the preceding segment. In its simplest form the 

 ovipositor consists of two strong ventral valves (v. v.), which 

 on being spread apart, expose the two inner valves (i. v.). The 

 latter constitute the main part of the ovipositor and are small, 

 sharp, slender pieces, which fit close together and so form a 

 channel through which the ova may be extruded. The tip 

 of the inner valves are barbed or sickle-shaped. The vagina 

 opens into the anterior end of the channel. Beneath the inner 

 valves are two large pieces which fit close together and compose 

 the dorsal valves of the ovipositor, (d. v.). 



The posterior region of the female abdomen as well as that 

 of the male, shows a great deal of variation in the modification 

 and advantage is taken of this for taxonomic purposes. The 

 ventral abdominal segment just anterior to the ovipositor 

 frequently shows a great deal of variation in shape. In the 

 majority of the forms examined, however, the essential details 

 of the female genital armature do not differ strikingly from the 

 above. 



In the male the last dorsal segment is known as the pygofer, 

 and as in the female, the anal tube opens on it. Ventrally, the 

 posterior of the abdomen is modified into a series of plates which 

 afford protection for the penis. The uppermost of these plates 

 is connected with the preceding abdominal segment and con- 

 stitutes the valve (g. v.) ; it is generally triangular in shape, and 

 extends about half way over the plates beneath. The latter are 

 the genital plates (g. pi.) and are two long, somewhat rectangular 

 pieces, which cover over the penis and penis guides. The 

 genital plates vary considerably in size and shape, and advantage 

 is taken of this character in the differentiation of species. In 

 copulation the ventral valve bends down so as to allow the 

 genital plates to spread apart, and the penis, with its accompany- 

 ing guides is brought into action. The penis (pen.) is an elongate 

 slender structure, which is strongly chitinized. It is hinged 

 at the base of the j^ygofer, and is capable of considerable motion 

 in a ventral direction. 



