FIELD BOOK OF INSECTS. 



length usually at least 1.5 in.; all edges of the pronotum 

 distinctly margined with yellow; elytra marked much like 

 verticalis but cross-bar more distinct; females usually have 

 the elytra grooved. Cybister fimbriolatus is about 1.3 in 

 long; brown with a faint greenish tinge; pronotum and 

 elytra broadly margined with yellow; front of head, two 

 front pairs of legs, and spots at sides of the third to sixth, 

 inclusive, abdominal segments yellow; pronotum and 

 elytra of female, except along the suture, with numerous, 

 fine, short grooves. 



POLYMORPHA 



The following family has also been put in the Adephaga. 



GYRINID^E 



All who observe have seen the steel-blue or black 

 Whirligig Beetles (Plate LXXIV, and p. 288) gyrating in 

 crowds on the surface of relatively still water or basking 

 like turtles on logs and stones. When disturbed, Whirligig 

 Beetles squeak by rubbing the tip of the abdomen against 

 the elytra. They also give off a fluid which is sometimes 

 ill-smelling but in other cases rather pleasantly suggests 

 apples. Although they spend most of their active time 

 on the surface of the water, they can fly well, if they can 

 climb out of the water so as to get a start, and they dive 

 freely, carrying down a bubble of air at the tips of, and 

 under, their elytra. The front legs are long and grasping. 

 Adults are, apparently, not very predaceous, but the 

 larvae .seem to be. The female lays a number of elongate, 

 oval eggs, end to end, upon the leaves of plants, usually 

 beneath the surface of the water and sometimes at a 

 considerable depth. The general appearance of the larva 

 is that of a small Centipede. The pupa of Gyrinus is so 

 well hidden that few have ever seen it. Probably about 

 the beginning of August the larva creeps out of the water 

 by climbing up the water-plants, and then spins a grayish 

 cocoon pointed at both ends, the adult emerging towards 

 the end of the same month. Adults hibernate, coming 

 out during mild weather for mid-winter dances. 



292 



