POISON-GLANDS OF THE MOSQUITO 



359 



of the glands ; the corroding active formic acid is the essential part 

 of the poison. (Will.) 



In Melipona the sting and poison-glands are aborted ; in certain 

 ants (Formica, Lasius, etc.) the sting is wanting, but the poison- 

 sac is extraordinarily large. 



Bordas finds in various species of Ichneumon three kinds of glands opening 

 into 'the base of the sting. The first two correspond to the acid (Fig. 348, 

 G.A) and alkaline {G.A) glands of bees and wasps (Vespidse, etc.), and the 

 third {G.ac) is situated between the two lateral muscular bundles which at- 

 tach the base of the sting to the last abdominal segment. The poison-reser- 

 voir (Fig. o48, V) is recognized by its yellow color and diaphanous and striated 

 appearance. It is situated on the left of the hind-intestine, a little in front 

 of the rectum. The tubular gland {Ga) or alkaline gland of aculeate Hyrnen- 

 optera is remarkably large ; it is situated on the left side of the body. The 

 accessory gland {G-.A) is elongated, triangular, flat, its duct opening at the 

 base of the alkaline gland ; it is formed of small spherical cells. Bordas has 

 met with well-developed poison-glands in forty species belonging to the Tere- 

 brantia, including that of Tenthredo, Emphytus, as well as varioTis genera of 

 IchneumouidEe, but in all these species the accessory gland was wanting. 



FIG. 350. View from above of the cephalic gland of Belostoma, x 20. This and Fig. 349 after Locy. 



Under the name of cephalic glands (Fig. 349), Locy describes 

 a pair of glands in the head of Nepidae. The epithelial or secreting 

 cells are 8-sided (Fig. 350). " When these insects are irritated," he 

 says, " a secretion is freely thrown out around the base of the beak, 

 which produces death very quickly when introduced on a needle 

 point into the body of an insect." He infers that the cephalic 

 glands may be the source of this poisonous secretion. The poisonous 

 salivary fluid of the larva of Dyticus is referred to on p. 324. 



That the mosquito injects poison into the wound it makes has 

 been proved by Macloskie, who discovering fine droplets of a yellow 

 oily-looking fluid escaping from the end of the hypopharynx, after- 

 wards detected the poison-glands. It appears that the two salivary 

 glands are subdivided, each into three lobes, the middle of which 

 (Fig. 351, pg) differs from the others in having evenly granulated 

 contents and staining more deeply than the others. Having exam- 

 ined the preparations, we agree with the discoverer that these lobes 



