356 r'.ULLETIN OF THE UNITED STATES FISH COMMISSION. 



These lar^e insects are not only provided wiLli powerful fore-legs 

 whicb the}' use to seize tlieir prey, and strong, somewhat oar-shaped 

 liind-legs for swiuiiuing ; but, when full-grown, they have strong wings 

 and are cajtable 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 difticult matter. Living, as they often do, in 

 pools which dry out at certain seasons of the year, this i)rovision 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 fouiul 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 tliey are found in these 

 situations from having been attracted to the reflecting surfaces of sky- 

 lights, for it is well known that water-beetles, with their imperfect sight, 

 mistake large expanses of glass, such as are presented by green-houses, 

 for sheets of water. Especially attractive, however, to these large water, 

 bugs are electric lights, and notices have api^eared in the daily press of 

 the swarming of these, as well as of other insects, about the electric 

 lights of cities. In flight, as Mr. Brackett states in the letter from 

 which I have already quoted, the species of Bclostomidw which he ob- 

 served can arise directly from the surface of the water. 



These insects differ, according to the species, as to their mode of egg- 

 laying. Some, like the common Zaitha fiuminca of our northern waters, 

 lay tlieir eggs on their own backs. In my collection I have a specimen 

 of this species which has her back almost entirely covered by a nicely- 

 arranged layer of elongated-oval, dark-brown eggs, which number over 

 a hundred and seventy-five. These eggs are set nicely upon one end, 

 and |)la(;ed in trausv^erse rows, by means of a long protrusile tube, or 

 ovipositor, which the insect can extend far over her own back. This 

 mode of oviposition insures the safety of the eggs until the young are 

 hat<;hed. The eggs are fastened to the back of the mother by a very 

 thin layer of a waterproof gum secreted by tlu; insect. The entire layer 

 of eggs is ai)t to split from the insects when they are dried, and con- 

 seqju^ntly is rarely seen in colleiitions of insects. The young bug 

 hat<'.hes from its eg^ by means of cutting out a round lid from tlie toi» 

 of the egg, an<l at about the time when theyoung brood begins tohatcth 

 the nu)thei' sImmIs the entire layer of eggs from her back, something as 

 she would molt, her skin during growth. It is i)robable that all the 

 species i\i' Zditha carry thtur eggs about with them, while, on the other 

 han<l, some, if not all, the si)ecies of BelosUnna deposit their eggs in 

 masses, under boards and logs, near the margins of the pools which 

 they inhabit. 



'V\\Q, young, upon hatching from the eggs, go immediately on their 

 preda(;eous course, often feedirig at first on young snails. As is true 

 of most hemiptera — the bugs ]»roperly s])eaking — the young differ little 

 from the adults except in the absence of wings in the former. In Belos- 



