Of the Hemiptera reported as attacking man, we shall consider briefly the forms most frequently noted. The NOTONECTIDÆ, or _back swimmers_, (fig. 19_b_) 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 BELOSTOMATIDÆ, or _giant water bugs_, (fig. 19_f_) include the largest living Hemiptera. They are attracted to lights and on account of the large numbers which swarm about the electric street lamps in some localities they have received the popular 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 œsophagus. On each side of the œsophagus there is a slender tube with a sigmoid swelling which may serve as a poison reservoir. In addition 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 Belostomatidæ feed not only on insects, but on small frogs, fish, salamanders and the like. Matheson (1907) has recorded the killing of a good-sized bird by _Belostoma americana_. A woodpecker, or flicker, was heard to utter cries of distress, and fluttered and fell from a tree. On examination it was found that a bug of this species had inserted its beak into the back part of the skull and was apparently busily engaged in sucking the blood or brains of the bird. Various species of _Belostoma_ have been cited as causing painful bites in man. We can testify from personal experience that the bite of _Belostoma americana_ may almost immediately cause severe, shooting pains that may extend throughout the arm and that they may be felt for several days. [Illustration: 20. Reduvius (Opsicœtus) personatus. (×2).]