194 ANATOMY. 



palus rujicornis), which doubtlessly retains the penis during copulation. 

 In the Capricorn beetles unprovided with an ovipositor (the Prionodea) 

 they are long, superiorly broader, pointed towards the apex, and gently 

 bending from each other. There are other forms in other insects. In 

 the orders possessing an ovipositor they appear as its valves, or as its 

 wings in those which possess only a vagina bivalvis, this leads us to the 

 investigation of the free sexual organs which project beyond the apex 

 of the abdomen. 



143. 



The free, exteriorly visible, sexual organs of female insects are of a 

 threefold description, at least three chief forms entomologists have dis- 

 tinguished by peculiar names, namely, the LAYING TUBE (vagina tubi- 

 formis), the LAYING SHEATH (vagina bivalvis), and the ACULEUS, 

 called also the TEREBRA, but which is one and the same organ with the 

 preceding. 



The LAYING TUBE (vagina tubiformis, PI. XXIV. f. 14.) is a mere 

 continuation of the abdomen, and consists, like it, of rings which gra- 

 dually decrease in compass, so that the largest and first, exactly as is 

 the case in the telescope, receives within it all the rest, when this organ 

 is withdrawn within the abdomen, wherein it lies concealed. These 

 rings are nothing else than segments of the abdomen itself, which have 

 adopted this altered shape and function in the course of the progressive 

 alteration of the relations of organisation. The proof that this opinion 

 is correct is shown in their number, for in the majority of cases (for 

 example, in the flies,) there are nine abdominal segments, when these 

 rings of the vagina are added to the visible ones of the abdomen. The 

 anal aperture also lies in this tube, which could not be the case if it 

 were merely an ovipositor. Thence, therefore, the last of these tubes 

 only can interest us here, from its containing the female organs. In 

 Cerambyx it is a leathery canal, of which that side nearest the venter 

 is supported by two horny ridges ; at the end of each bone there is a 

 short two-jointed process, the first joint of which is large, thick, bulb- 

 ous, and armed on the exterior with short spines ; the second, however, 

 is small and round, and has two stiff setae at its extremity. In the 

 flies, which all possess a tubiform vagina, its last joint has above a 

 horny plate, to which also two short single-jointed, hook-shaped, 

 crooked processes hang attached. The tubiform vagina of the ruby 

 tails (Chrysis) appears, as far as I have been able to ascertain from 



