FEMALE ORGANS OF GENERATION. 193 



strong thorns; in the Capricorn beetles (Cerambycina) it is elongated 

 into a horny, many-jointed ovipositor. In Hydropkilus it runs out 

 on each side into a horny point, which Suckow * considers as the 

 analogue of the clitoris. In Melolontha the vagina has on each side a 

 small pocket, into which the lateral wings of the penis pass during co- 

 pulation, which explains the cause of the protracted union of this insect. 

 In all insects provided with an aculeus or an ovipositor, the vagina 

 opens at its base, so that its canal passes directly into that of the ovi- 

 positor. The valves and spines of this apparatus are consequently 

 nothing more than the horny bone which lies within the vagina, and 

 which is then prolonged beyond it. 



B. EXTERNAL SEXUAL ORGANS. 



142. 



The external sexual organs of insects do not always project beyond 

 the apex of the abdomen, but usually lie in the cavity into which the 

 orifice of the anus and of the vagina open. This cavity, common to 

 both, is formed of two valves, the one larger, lying upon the dorsal side, 

 and the other smaller, upon the ventral side, and beyond which the 

 former projects all round. These two valves, which are not visible 

 exteriorly, but are enclosed by the dorsal and ventral plates of the last 

 abdominal segment, are evidently nothing but the last segment itself, 

 those called the last being the last but one. It is only thus that we can 

 explain the disappearance of the segments of the larva in the perfect in- 

 sect, in which we shall also generally discover nine segments if we include 

 the last concealed one. But where there are nine visible segments 

 the last is not then concealed, but free. It is within this last abdominal 

 segment, whether it be concealed or free, that the orifice of the vagina is 

 found, and indeed, beneath the anus, divided from it only by a projecting 

 plate. The entrance itself is opened, mostly by horny substances, which 

 have partly been described in the preceding paragraph in the description 

 of the vagina. The lateral horny ridges, namely, becdme more elongate, 

 so that they project as far as the limits of the valves, gradually 

 separating, and thus forming a spacious entrance. The length of the 

 vagina depends upon that of these horny ridges ; they are short in the 

 Carabodea, and often armed at their apex with a strong hook 



* Reusing. Zeitschr. vol. ii. p. 254. 

 O 



