BULLETIN or J'lIE UNITED STATES FI8TI COMMISSION. 357 



t(ntia tlie youiiji', liowcvcr, liavc two claws on (lie tarsi ol' tlir foro l«'j;s, 

 wliik' as adults they have *>nly one tarsal claw in tlic same j)lacc. It is 

 uot <'A'rtaiiily known, but it is likely tliat these insects reach their lull 

 growth in a year. 



lu seizing upon lishes or other small animals these insects grasp their 

 prey with their fore feet, holding it firmly in their claws, then piercing 

 it with their beak or proboscis ; for they only suck blood, not being 

 able, as is the case with water-beetles, to eat the whole animal. The 

 proboscis consists of stout horny setic or bristles which tit closely to- 

 gether to form a fine sucking-tube, while the exhaustion is perlormcd 

 by means of a muscular, extensible pharynx, or throat. As is probably 

 the case with all carnivorous hemiptera, only living i)rey is acceptable 

 to these insects. The predaceous m ater-bugs are said to destroy the 

 eggs of fishes, although further confirmation of this statement is desir- 

 able. 



When the water bugs attack other aninjals it is noticeable that the 

 ])rey dies much quicker than it would normally do from simi)ly the loss 

 of blood consequent upon the sucking of the bug, so it is generally sup- 

 posed that these insects inject a poisonous secretion through tlieir pro- 

 boscis into the wound they make. Most of these insects intlict <iuite 

 severe stings, in self-defense, if they are handled too freely, using the 

 proboscis for this purpose. Leidy^ describes the salivary glands of 

 Belostoma, which are well developed, and it is undoubtedly the secre- 

 tion of these glands that iioisons the prey when it is i)ierced by thei)ro- 

 boscis. 



As will be seen from the preceding part of this paper, the destruction 

 of the bugs that attack fishes is uot an easy matter. The water-beetles 

 can be trapped by the use of decaying animal matter, of which thej'ure 

 very fond. I have seen a dead rat in a small pond surrounded by a great 

 number of these beetles {Dytiscidcc), and they prefer such food to living- 

 food. On the other hand, the water-bugs will take only living food, so 

 that their entrapping by any bait would be difficult. 



The use of poison for aquatic hemiptera seems also impracticable. 

 As hemiptera eat only liquid food which they can suck up through the 

 fine tube of their proboscis, poison that would have any effect upon them 

 must be a liquid, a very finely-divided substance held in suspension in 

 a liquid, a corrosive substance that will directly attack the surface of 

 the bug, or some substance that gives off poisonous vapors. The above 

 remark applies to all hemiptera, but the destruction of aquatic hemip- 

 tera is still more difficult. In their case no liquid poison can be ai)pli('d, 

 because the bugs would not eat it, and because its mixture with water 

 would endanger the fish that it was sought to protect. For like rea- 

 sons no corrosive substance or poisonous vapor is applicable. Water- 

 bugs are so much hardier than fish that nothing dissolved in the water 

 would injure them that would not prove dangerous for the fish 



