236 



FAMILY V. GYKINIDJE. 



462 (1502). Cybister fimbkiolatus Say, Trans. Airier. Phil. Soc, II, 1823. 

 9; ibid. II, 506. 



Ovate, more or less wedge-shaped. Above brown with a faint greenish 

 tinge; thorax and elytra with a broad yellow margin; front of head, four 

 front legs and spots at sides of abdominal segments 3 to 6, also yellow. 

 Thorax and elytra of female, except along the suture, with numerous fine 

 short impressed lines. Length 30-33 mm. 



Throughout the State; frequent. May 27-September 20. In 

 autumn sometimes found beneath rubbish on the beaches of lakes. 



Family Y. GYRINILLE. 

 The Whirligig Beetles. 



In the little bays of lakes and ponds and along the quiet places 

 of flowing streams one often sees, close into shore, large colonies 

 of beetles playing and gyrating upon the surface of the still water. 

 These beetles are oval or elliptical in form, somewhat flattened, more 

 or less attenuate at either end and usually of a brilliant bluish-black 

 color. The name of the family is founded upon the principal 

 genus Gyrinus, which in turn is derived from a Greek word mean- 

 ing "a circle," and given to these insects on account of their habit 

 of moving in little circles upon the surface of the water. They do 

 not swim, as commonly stated, but glide or skate upon the surface- 

 film of the water in the same manner as do the wherrymen or water- 

 spiders among the Hemiptera. Except when pursued they rarely 

 dive beneath the surface, and they then carry with them a small 

 supply of air and stay but a short time. Being so agile they are 

 difficult to capture even with a net, When handled they exude a 

 milky fluid which usually has a disagreeable odor, but in certain 

 species resembles that of ripe apples, hence they are sometimes 

 called "apple bugs." 



Some of the species occasionally crawl out of the water onto logs, 

 stones or other objects, where they bask in the sunlight. If ap- 

 proached when so engaged, they let go all hold and tumble, instead 

 of crawling back into the water, much in the same way as does a 

 basking turtle. When undisturbed, the colonies or groups are 

 usually massed close together, and are sometimes almost quiescent, 

 The least alarm will, however, cause a large, closely bunched assem- 

 bly to scatter widely in all directions. 



From the margins of these groups individuals are continually 

 darting out for a short distance, then back" again. These little jour- 

 neys are probably made in search of prey, as the beetles snap vigor- 



