274 
COLEOPTERA. 
abundant in freshwater in India, especially if stagnant or nearly so. 
Pupation takes place in the mud near the water. The adults are 
aquatic, and carry their air supply under their elytra ; they also 
come up periodically with the apex of the elytra upwards to renew 
their air supply. They are carnivorous but less voracious than the 
larvae and fly at night from pond to pond. Nothing is known 
of the habits of the Indian species nor of their mode of hibernation, 
number 
Fig. 155.— Eretes sticticus larva and imago x 3. 
Sharp in 1876 experimented with Dytiscidce to find the ratio of the 
time spent getting air at the surface to that spent under water. He 
found in Dytiscus marginalis a ratio of 1 to 12. Pelobius has a ratio of 
1 to 375. (Proc. Linn. Soc., 1877.) 
The family is a large one, monographed by Sharp (On Aquatic 
Carnivorous Coleoptera) ; Kegimbart in 1899 revised the Eastern forms 
(Ann. Soc. Ent. France, 1899, p. 186) listing 140 “ Indian ” species. 
Three new ones collected by Maindron were added (loc. cit., 1903, p. 
333). The principal genera are arranged as follows :— 
