DYTISCID.E. GYBJNIDiE. 



65 



the cerci and anal appendages, number of joints of the antennas, 

 etc., and, in some species (e. g. Hyphydrus ferrugineus) the head 

 is produced into a distinct horn, which is touched at about three 

 quarters of its length from the base by the tips of the mandibles. 



The Dytiscid^: are for the most part characteristic of the Paiae- 

 arctic region and seem to prefer, as a whole, cold to warmer 

 water ; they are, however, found all over the globe, and occur in 

 brackish and more or less salt w 7 ater as well as 

 in fresh, in running streams or stagnant pools, 

 and one or two species have been found in 

 thermal springs. In all, about 1800 or 2000 

 members of the family are known. The Indian 

 species appear to have been very little 

 worked and the following genera are almost 

 the only ones that seem to be at present 

 known as occurring in the country : — Dytiscus 

 (IVogus), Hydrocoptus, Laccophilus, Hydro- 

 Tig. 29.— Hydaticus vatus (several species), Cybister, Hyphydrus, 

 festivus. Hydaticus, Hyphoporus, Platynectes, Lacconectus, 



Bidessus, Copelatus, Cantliydrus, and the con- 

 spicuous and gaily coloured Sandracottus which are confined to 

 India, Eastern Asia, the Malay Eegion, and Australia. 



Family 7. GYIilNIDiE. 



Anlennm inserted under the side margins of the forehead behind 

 the base of the mandibles, very short and thick, eleven-jointed, the first 

 cylindrical and cup-shaped, the second ear-shaped and dilate on its 

 margins, and the rest forming a closely adpressed club ; eyes entirely 

 divided into four ; metasternum without suture ; middle and 

 hind legs both forming short broad paddles ; abdomen ivith seven 

 visible ventral segments, the first two closely united at the sides, 

 connate in the middle. 



These insects, commonly called " Whirligig Beetles," are well 



known to all observers ; they are 

 found, usually, in groups on the 

 surface of the water, on which they 

 swim with great rapidity, so swiftly 

 in fact that the eye can hardly 

 follow their motions. If much 

 alarmed they dive below the surface 

 of the water, but seem unable to 

 keep down for more than a short 

 time and soon reappear. The 

 females, as a rule, are larger and 

 duller than the males ; the latter 

 have the whole of the joints 

 of the anterior tarsi dilated and 

 furnished with very small round transparent suckers. 



Fig. 30. — Dineutes indicus; 

 and head, showing divided eyes. 



