ORDER COLEOPTERA: BEETLES 235 



these are largish water-beetles, with oval, somewhat flattened 

 bodies, polished elytra, and feathered hind legs adapted for 

 swimming: the larva (Fig. lOo), which also is aquatic, has 

 enormous channelled mandibles like those of the ant-lions, 

 for seizing and sucking prey, and a tapering abdomen which 

 ends in a pair of feathered lobes or filaments, the last 2 

 abdominal segments also being feathered. 



Of the Clavicornia eight families may be introduced 

 to the medical officer, namely : — (a) Gyrinidce, or whirligig- 

 beetles, the adults and larvae of which are aquatic and 

 predaceous and may possibly (as may the DytiscidcB) devour 

 mosquito-larvae. The whirligigs are often seen disporting 

 in companies on the surface of the water, occasionally taking 

 a sudden dive ; the antennae are short and blunt, and the 

 middle and hind legs are paddles for swimming ; the larva 

 (Fig. loi) is long and slender, with a pair of gill-filaments 



Fig. 101.— Aquatic Larva of Gyrinnt (copied from MiaU). 



on each of the first 8 abdominal segments, two pairs on the 

 9th, and two pairs of hooks on the small loth segment, 

 (b) HydrophilidcE — these also are water-beetles, and can be 

 distinguished both from Dytiscidm and Gyrinidce by their 

 antennae, which are long and clubbed and consist of 9 distinct 

 segments : the aquatic larva, which is rapacious, has neither 

 the enormous channelled mandibles of Dytiscus, nor the 

 feathered tracheal gills of Gyrinus, and its tapering abdomen 

 ends in a pair of segmented hooks, (c) Ptatypsyllidce — small 

 blind beetles, with short elytra and no wings, and antennae of 

 3 segments, the 3rd being impacted in the 2nd ; parasitic 

 in the fur of beavers, (d) LeptinidcB — small beetles, blind or 

 with imperfect eyes, with properly formed elytra, and 

 antennae of 1 1 segments ; parasitic on beavers and other 

 smaller rodents, (e) Silphida — burying-beetles, with knobbed 

 antennae ; well known by their habit of mining beneath and 

 ultimately burying the dead bodies of small animals ; the 



