BULLETIN OF THE UNITED STATES FISH COMMISSION. 355 



Belostoma grande. — After Riley. 



ently bad been feeding on them. I bad no means of determining bow 

 many of these bugs were in the jiond." 



The largest, and without doubt the most dangerous to fishes, of these 

 water-bugs are those whicli bek>ng to a family 

 called by naturalists Belostomiclw. It is especi- 

 ally of these Bdostomidw that this paper treats. 

 In the northeastern United States the common 

 forms of these bugs belong to tbcgencraZai^/ia, 

 Belostoma, and Bcnacus. The accompanying 

 figure of one of the species of Belostoina, which 

 genus in the tropics contains some veritable 

 giants in the insect line, will give a good gen- 

 eral idea of the form and appearance of these 

 insects. The species fig u red , B. grande, is found 

 intemperate and tropical parts of North Amer- 

 ica. Tbe form of insects belonging to the genus 

 Belosfoma is elongated oval, and their consider- 

 ably flattened form and large size serves to dis- 

 tinguish them from all the other before- men- 

 tioned water bugs except those belonging to 

 the genus Nepa, and from them they are easily 

 distinguished by the fact that the body of Nepa 

 terminates in a long tube formed by the apposition of two grooved ap- 

 pendages; through this tube the insect obtains air for breathing, while 

 the species of Belostoma have no such tube. The form in Zaitha is like 

 that of Belosfoma, but the species are smaller. In Benaciis, another 

 closely allied genus, of which the sole species, B. haldemannm, is found 

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

 forward side, a groove whicli is present in the species of Belostoma, and 

 which serves for the partial reception of the tibia when the fore-leg is 

 folded up. Tbe genera Zaitha and Benacus formerly were considered 

 to be a part of the genus Belostoma. 



Insects of tlie family Belostomidw are abundant in nearly all parts of 

 tbe tropical and temperate zones of both hemispheres, except in Euro])e, 

 where they are extremely rare ; but, as a general rule, these insects are 

 larger tbe warmer tbe climate in which they live. Individual s]>ecimens 

 of Belostoma grande are sometimes found in tropical America which 

 measure 4 inches in length, and B. griseum, which is found in the north- 

 ern United States, attains a length of 3^ inches. Tbe young of this 

 species when only two days from the Q^g measured, according to Pack- 

 ard, a third of an inch in length. 



The color of the species of Belostomid/c is brown, of a greater or less 

 depth, or of a yellowish or a greenish shade. Partially covered with 

 mud, they are quite difficult to discover. Tbe sexes are not easy to dis- 

 tinguish from one another, except that females can at times be distin- 

 guished by tbe eggs which thej' carry. 



