192 ANATOMY. 



and egg or pear-shaped one, which discharges itself into the duct by a 

 narrow canal, is the spermatheca; the other four are vascular gluten 

 glands. In Fanessa Urtlcce they are short, the anterior one broader 

 than the posterior, both discharge themselves into the duct at one part 

 but at opposite sides, before the spermatheca ; in Gastrophaga Pini 

 (PI. XXVIII. f. 4.) they are very long, and the anterior as well as the 

 posterior unite into a simple but very short canal. The anterior one, 

 which discharges itself close in front of the spermatheca, is distended 

 in the middle into a bladder ; in the posterior ones, which discharge 

 themselves into the vagina, this vesicular distension takes place at the 

 end of each single tube before they unite into a common duct. 



The poison vessels of the Hymenoptera aculeata are appendages of a 

 peculiar description. In them a round, perfectly ovate bladder (PL 

 XXVIII. f. 5, 6. b, 6), with a narrow duct, discharges itself into the 

 sting, which we shall describe below ( 145). This bladder lies quite 

 at the end of the abdomen close to the orifice of the sexual organs. It 

 contains a bright clear fluid which is secreted by two either long very 

 fine, much twisted vessels, or of shorter ones, originating from a fasci- 

 culus of furcate vessels (Pompilus*}, which opposite the orifice sink 

 into the bladder, and either separated as far as their orifice, as in 

 Vespa crebro (PL XXVIII. f. 6. a, ), or as in Apis mellifica (f. 5. 

 a, a), are united into one vessel, a little distance before the connexion 

 with the bladder. May not the posterior vessels of the Lepidoptera, 

 which we have just described, be analogous to these, and both be pro- 

 perly considered as organs secreting urine ? 



141. 



THE VAGINA. 



The last portion of the common evacuating duct lying behind the 

 egg-evacuating duct is called the VAGINA. It is a short direct tube, 

 narrower than the egg canal but wider than the oviduct. Its function 

 being to receive the penis of the male and to assist in depositing the 

 eggs, it is, like all the other organs of insects which require constant 

 distension, held in this state by horny leaves and ridges. There are 

 generally three such horny plates, one above, one lateral, and one be- 

 neath. In Harpalus the superior plate is a thin bone, which towards 

 the exterior distends in the shape of a shovel, and is there armed with 



* Ramdohr, Verdauungsorgane, PI. XIV. f. 5, 



