54 



ENTOMOLOGY 



roach olfactory, while the cerci of male Acridiidse often serve to hold the 

 female during copulation. 



Extremity of Abdomen. Various modifications of the terminal 

 segments of the abdomen occur for the purposes of defaecation and es- 

 pecially reproduction. The anus, dorsal in position, opens always through 

 the last segment and is often shielded above by a suranal plate and on each 

 side by a lateral plate. The genital orifice is always ventral in position 

 and occurs commonly on the ninth abdominal segment, though there is 

 some variation in this respect. The external, or accessory, organs of. re- 

 production are termed the genitalia. 



Female Genitalia. In Neuroptera, Coleoptera, Lepidoptera and 

 Diptera the vagina simply opens to the exterior or else with the anus into 

 a common chamber, or cloaca. Often, as in Cerambyx (Fig. 77) and 

 Cecidomyia (Fig. 78) the attenuated distal segments of the abdomen serve 



the purpose of an ovipositor; 

 6 thus in Cecidomyiidae, the ter- 



r minal segments, telescoped into 



FIG. 77. Abdomen of female beetle, Cer- 

 ambyx, in which the last three segments are 

 used as an ovipositor. After KOLBE. 



FIG. 78. Abdomen of a female midge, 

 Dasyneiira legnminicola, to show the 

 pseudo-ovipositor. 



one another when not in use, form when extruded a lash-like organ ex- 

 ceeding frequently the remainder of the body in length. 



A true ovipositor occurs in Thysanura, Orthoptera, Odonata, Hemip- 

 tera, Hymenoptera and some other orders of insects. The ovipositor con- 

 sists essentially of three pairs of valves, or gonapophyses a dorsal, a 

 ventral and an inner pair. The two inner valves form a channel through 

 which the eggs are conveyed. In Locustidae (Fig. 79) the three valves of 

 each side are held together by tongues and grooves, which, however, 

 permit sliding movements to take place. Most authorities have found 

 that the gonapophyses belong to the segmental series of paired appen- 

 dagesare homodynamous with limbs and pertain commonly to ab- 

 dominal segments seven, eight and nine. 



The ovipositor attains its greatest complexity in Hymenoptera, in 

 which it becomes modified for sawing, boring or stinging. In Sir ex (Fig. 

 80) the inner valves are united; in Apis the dorsal valves are repre- 

 sented by a pair of palpi, the inner valves unite to form the sheath 



