FISH-DESTROYING BUGS. 103 



Nepa, and from them they are easily distinguished by the fact 

 that the body of Nejxi terminates in a long tube formed by the 

 apposition of two grooved appendages ; through this tube the 

 insect obtains air for breathing, while the species of Belostnma 

 have no such tube. The form in Zaitha is like that of Belostoma, 

 but the species are smaller. In Benacus, another closely allied 

 genus, of which the sole species, B. haldemamim, is found in the 

 United States, the femur of each fore-leg lacks the groove on its 

 forward side, — a groove which is present in the species of 

 Belostoma, and which serves for the partial reception of the tibia 

 when the fore-leg is folded up. The genera Zaitha and Benacus 

 formerly wei'e considered to be a part of the genus Belostoma. 



Insects of the family Belostomidae are abundant in nearly all 

 parts of the tropical and temperate zones of both hemispheres, 

 except in Europe, where they are extremely rare ; but, as a. 

 general rule, these insects are larger the warmer the climate in 

 which they live. Individual specimens of Belostoma grande are 

 sometimes found in tropical America, which measure four inches 

 in length, and B. gr'iseum, which is found in the northern 

 United States, attains a length of three and a half inches. The 

 young of this species when only two days from the egg measured, 

 according to Packard, a third of an inch in length. 



The colour of the species of Belostomidse is brown, of a 

 greater or less depth, or of a yellowish or a greenish shade. 

 Partially covered with mud, they are diflBcult to discover. The 

 sexes are not easy to distinguish from one another, except that 

 females can at times be distinguished by the eggs which they carry. 



These large insects are not only provided with powerful fore- 

 legs which they use to seize their prey, and strong, somewhat 

 oar-shaped hind-legs for swimming; but, when full-grown, they 

 have strong wings and are capable of long-sustained flight. By 

 their flights, which, as in most aquatic Hemiptera, take place 

 at night, these insects pass from one pond to another. This 

 insures them a wide distribution, and makes their extermination 

 a difficult matter. Living, as they often do, in pools which dry 

 up at certain seasons of the year, this provision for flight is a 

 necessity of their existence. That these flights are often long 

 and high is proved by the fact that the bugs have been found in 

 the midst of large cities, far from any pond or pool, upon the 

 roofs of three and four story blocks. It is probable that they 



