210 ENTOMOLOGY FOE MEDICAL OFFICERS 



bugs belonging to other families are also known to bite man 

 occasionally. 



5. Family HVDROMETRlDyE : Pond-skaters, or Water- 

 striders. The bugs of this family skim about on the surface 

 of water, often in companies, and usually have very long legs. 

 They prey upon aquatic insects, etc., and may be regarded as 

 potential enemies of mosquitoes and mosquito-larvae. The 

 species of Halobates live on the surface of the ocean, often 

 many hundreds of miles from land. 



{b) Heteroptera Cryptocerata. 



The true water-bugs with concealed antennae are all 

 predaceous, and may possibly include mosquitoes and 

 mosquito-larvse in their prey; moreover, some of them when 

 handled can give a very shrewd "bite," that of the giant 

 water-bug {Belostomd) being -well known in India as en- 

 venomed. The following are the several families : — 



(i) GalgulidcE ; squat toad-shaped bugs, with prominent 

 eyes, that frequent marshy places in most parts of the world : 

 the legs are of the ordinary form for crawling. (2) Nau- 

 coridcB ; flat, oval bugs which, though truly aquatic, have not 

 the legs modified for swimming ; they are distinguished from 

 the Galgulidae by (among other things) the absence of ocelli. 

 (3) Nepidce, or Water-scorpions, common in stagnant waters 

 everywhere ; the long front legs are raptorial and the 

 abdomen ends in a long slender breathing-tube formed of 

 two lateral separable pieces ; in one genus, Nepa, the body is 

 leaf-like, in the other genus, Ranatra, it is more like that of a 

 stick-insect. (4) BelostomatidcB, Giant water-bugs, common 

 in stagnant water in tropical and sub-tropical countries ; the 

 body is oval and flat and the legs are flattened for swimming ; 

 there is no breathing-tube at the end of the abdomen ; some 

 of the species are large enough to overpower frogs and fish ; 

 the "bite" of Belostoma is very painful. (5) Notonectidm, or 

 Water Boatmen ; oval bugs with very long, feathered hind legs ; 

 they swim on their back. (6) Corixidcs ; much like water 

 boatmen, but they swim right way up, and have the beak 

 concealed and apparently unsegmented, the beak of the 

 water boatmen being free and consisting of 3 or 4 segments. 



