REPORT ON MOSOUITOES. 



89 



These seem to be the only beetles that have any decided effect 

 in controlHng mosquito larva? and, while the water tigers are 

 not particular as to the kind of place in which they breed, yet it 

 must be reasonably permanent and they prefer it clean. They 

 occur, however, in the brackish pools in the salt marshes. The 

 whirligig beetles are useful only on large bodies of clean water ; 

 but their influence on the development of AnopJielcs is very de- 

 cided. Neither of the groups reach the breeders in temporary 

 rain-water pools nor those that live in foul water. 



Figure 21. 



A Water-boatman; Notonecta species. 



Among the water bugs there are several species that form 

 effective checks to mosquito breeding. Nearly all the predatory 

 species will take mosquito larvae and, usually, where the back- 



Figure 22. 



A Water-strider, Rheumat abates rilcyi, female, a, anterior tarsus; h, ovipositor; c, 

 posterior tarsus, all much enlarged. (From "Insect Life," U. S. Dept. Agric.) 



