INSECTA. 



991 



short valvular projectile organ, covered exter- 

 nally by two pointed horny plates (i), clothed 

 with soft hairs. Above these are two other 

 irregular double-jointed plates (/), convex on 

 their outer and concave on their inner surface, 

 and surrounded at their base by a bony ring 

 (A-). They are half corneous half membranous, 

 and folded together like a closed fan, and are 

 furnished at their posterior margin with horny 

 hooks (i), which are used as organs of prehen- 

 sion. Between these in the middle line are 

 two elongated muscular parts (w), which when 

 applied together form a pointed structure, and 

 inclose between them in its retracted state the 

 proper intromittent organ (A). These perhaps 

 assist to dilate the vulva of the female, like the 

 plates above noticed in the Coleoptera. In 

 many instances, as in Anthidium momentum, 

 the posterior margin of the last true abdominal 

 segment is armed with spines that are curved 

 downwards, and serve to retain the female, and 

 this is also the case in the Ckryudidsf. In 

 Anthophora return the horny penis formed of 

 the last two segments of the larva has also two 

 external plates developed into hooked prehen- 

 sile organs, with which the insect grasps the 

 abdomen of the female at the moment of actual 

 connexion. In the Sphinx f^g.391) and other 

 Lepidoptera the appendages of the anal seg- 

 ment appear to be analogous to the sheath of 

 the ovipositor in the preceding orders. On 

 each side of these parts at their inner surface 

 are two horny plates, which form the lateral 

 boundary of the male organs. Within these is 

 a cloaca, in which the anal aperture terminates, 

 and immediately beneath it are situated the 

 male organs. These consist of an extensile 

 bind, ejaculatory organ included between two 

 soft valvular parts. They form the virile 

 organ. In the Sphinx the posterior margin of 

 the dorsal plate of the terminal segment is 

 armed with a slender curved hook, bifid at its 

 apex, and bent downwards, like the hooks in 

 the body of Hymerioptera, for retaining con- 

 nexion with the female. Among the Diptera 

 the Asilida: have the male organ formed in a 

 somewhat similar manner. The terminal seg- 

 ment of the body forms a pair of broad horny 

 plates, which inclose between them the double 

 stiliform excretory canal. 



The duclitfi cjaculatorius passes backwards 

 from the penis as a single canal, which either is 

 exceedingly short, as in Athalia, (fig. 437,/J, 

 or is a very long tube, forming many convolutions 

 in its course, as in many of the Coleoptera. 

 Into this canal open the vesicnla aernijiales and 

 the vasa deftrentiu. The vesicula seminales are 

 usually long convoluted ccecal tubes, which 

 assume a variety of forms, sometimes branched 

 sometimes simple. They are two, and some- 

 times four in number. In some species, as in 

 Athalia (e}, they are exceedingly short, and 

 very much dilated, serving evidently as recep- 

 tacles for the semen as it is secreted by the 

 testes, and conveyed towards the ejaculatory 

 duct by the vasa deferentia (d). These, like 

 the seminal vessels, vary in number according 

 to the number of the testes. When the whole 

 of the testes are aggregated together, the vasa 



deferentia that proceed from them are united 

 from each set of testes into a single tube on 

 each side (6), but when the testes remain dis- 

 tinct from each other, each deferential vessel 

 passes at first separately from each testis for a 

 short distance, and the whole are then collected 

 together, and form on each side a single tube, 

 which, after many convolutions, either is in- 

 serted into the extremity of the seminal vessel, 

 or is inserted along with it into the commence- 

 ment of the ejaculatory duct. The length of 

 the common deferential vessels is sometimes so 

 great, and they are so much convoluted, as to 

 be readily mistaken for testes, much larger than 

 the proper testicles. This is the case in Athalia 

 (d}. The proper testes are usually several 

 rounded glandular bodies, in some instances, as 

 in Melulontha* and Lucanus, amounting to as 

 many as six on each side, and in a few in- 

 stances, as in Athalia, even to as many as thir- 

 teen. In form they are sometimes rounded, and 

 sometimes are elongated cceciform tubes. They 

 are usually regarded as ccecal organs, but in 

 some instances we have distinctly traced minute 

 vessels connected with them, but whether these 

 vessels passed by open mouths directly into the 

 coeca, or whether distributed over their surface, 

 is perhaps still a question ; our impression cer- 

 tainly is that they enter the testes. Besides 

 these parts, there are in some instances struc- 

 tures that resemble an epididymis, as in Hy- 

 dromfi but these are generally absent. 



These organs lie within the abdominal cavity, 

 in general on each side of the alimentary canal, 

 and sometimes above it, as in the instance of 

 the Lepidoptera, in which the two separate 

 testes of the larva (fig- 364, i) are united in 

 the perfect insect into one mass, which is situ- 

 ated immediately beneath the dorsal vessel 

 (Jig- 366, *'). In each of these cases the con- 

 nexion with the vessel, as formerly noticed, is 

 distinctly traced. Besides these parts we ought 

 also to notice some which are appendages of 

 the organs similar to appendages found in the 

 female, but the function of which is not dis- 

 tinctly understood. 



In the female the organs of generation are 

 more simple than in the male. Of these we 

 have first to notice those external parts which 

 form, as we have stated, either the long ex- 

 tended ovipositor of the GrryUufa, the sheath 

 of the sting of the bee (fig. 438, A, a,d), or 

 the sheath or valves of the ovipositor of the 

 Terebrantia (C, b}. The condensed descrip- 

 tion of these parts that has been given by Mr. 

 WestwoodJ clearly explains their structure. 

 He remarks that, " from the centre of the 

 under side of the abdomen, near its extre- 

 mity, arise two plates, each consisting of 

 two joints, sometimes valvular and together 

 forming a scabbard, sometimes more slender, 

 and resembling palpi, and sometimes very 

 long ; between these plates, as they exist in the 

 bee (A, 6), under the form of two flattened 

 plates, with a pair of terminal lobes, arise two 

 other pieces which are very slender, serrated 



* Straus, 

 t Dufour. 

 t Entomologist's Text Book, p. 375. 



