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TEXT-BOOK OF ENTOMOLOGY 



alkaline fluid, the other an acid product. The poison is only effec- 

 tive when both fluids are mixed. The resultant venom is always 

 acid. The action of this venom upon some animals, as rabbits, frogs, 

 and certain beetles, is slight; but the domestic fly and the flesh-fly 

 are immediately killed by it. The inoculation of a fly with the 

 secretion of one of the glands does not produce death until after a 

 considerable time, but death follows very quickly if the same fly 

 is subjected to a second inoculation, this time with the secretion 

 of the other gland. The alkaline glands are in bees and all poison- 

 ous Hymenoptera strongly developed, but become vestigial in those 

 forms which sting their prey to serve as food for their larvae. The 



poison which the solitary sand and 

 wood wasps and Pompilidae inject 

 into their victims only paralyzes them. 



Fio. 848. The poison apparatus of 

 Ichneumon : T, sting ; GA acid gland ; 

 TG, R\ its tubes opening into the com- 

 mon poison-sac or reservoir ; ce, its effer- 

 ent canal ; Ga, the tubular alkaline gland ; 

 H, the glandular end ; a, the reservoir ; 

 ce, its duct ; Gae, the accessory gland 

 After Bordas. 



EYE 



CEPHALIC GLANDS 

 FIG. 349. Cephalic gland of Belostoma. 



Bordas has found both the alkaline gland (gland of Dufour) and the acid 

 gland to occur in a hundred species of Hymenoptera, including not only Aculeata, 

 but also Ichneumonidse (Fig. 348), Tenthredinidse, and they may be safely said 

 to be of general occurrence. The acid gland consists of three parts, the glandular 

 portion, the reservoir for the poison, and the secretory canal. The alkaline 

 gland is an irregular tube, with a striated surface and without a reservoir. In 

 most Hymenoptera there is still a third gland, which is unpaired, granular, rec- 

 tangular or lanceolate, with a short filamentous duct which opens beside the 

 orifice of the alkaline glands. 



The poison in ants, wasps, and bees consists of two substances, 

 i.e. formic acid and a whitish, fatty, bitter residue in the secretion 



