30 Poisonous Arthropods 



made up of a dilatation forming the body of the pump, in which there 

 is a chitinous piston. Attached to the piston is a strong retractor 

 muscle. The function of the salivary pump is to suck up the saliva 

 from the saHvary ducts and to force it out through the beak. 



Of the Hemiptera reported as attacking man, we shall consider 

 briefly the forms most frequently noted. 



The Notonectidae, or back swimmers, (fig. 19&) are small, aquatic 

 bugs that differ from all others in that they always swim on their 

 backs. They are predaceous, feeding on insects and other small 

 forms. When handled carelessly they are able to inflict a painful 

 bite, which is sometimes as severe as the sting of a bee. In fact, 

 they are known in Germany as " Wasserbienen. " 



The Belostomatidae, or giant water bugs, (fig. 19/) include the largest 

 living Hemiptera. They are attracted to lights and on accoimt of the 

 large numbers which swarm about the electric street lamps in some 

 localities they have received the popvilar name "electric light bugs." 

 Our largest representatives in the northern United States belong to 

 the two genera Belostoma and Banacus, distinguished from each 

 other by the fact that Belostoma has a groove on the under side of 

 the femur of the front leg, for the reception of the tibia. _ 



The salivary glands of Belostoma were figured by Leidy (1847) 

 and later were studied in more detail by Locy (1884). There are 

 two pairs of the glands, those of one pair being long and extending 

 back as far as the beginning of the abdomen, while the others are 

 about one-fourth as long. They lie on either side of the oesophagus. 

 On each side of the oesophagus there is a slender tube with a 

 sigmoid swelling which may serve as a poison reservoir. In addi- 

 tion to this salivary system, there is a pair of very prominent glands 

 on the ventral side of the head, opening just above the base of the 

 beak. These Locy has called the "cephalic glands" and he suggests 

 that they are the source of the poison. They are the homologues 

 of the maxillary glands described for other Hemiptera, and it is by 

 no means clear that they are concerned with the production of 

 venom. It seems more probable that in Belostoma, as in other 

 Hemiptera, it is produced by the salivary glands, though the question 

 is an open one. 



The Belostomatidae feed not only on insects, but on small frogs, 

 fish, salamanders and the like. Matheson'(i907) has recorded the 

 killing of a good-sized bird by Belostoma americana. A woodpecker, 



