THE CLICK BEETLES. 



699 



Family XXXVII. BLATERID.^. 

 Click Beetles. Speing Beetles. Snapping Bugs. Skipjacks. 



Every country boy in Indiana has found beneath the bark of 

 logs or stumps either a big grayish-black beetle an inch or more in 

 length, or smaller, slender brown ones, which feign death when first 

 picked up, but, when placed on their backs, after a few seconds give 

 a click, and spring several inches into the air, turn over in their 

 descent, alight on their feet and crawl rapidly away. These beetles 

 are typical representatives of the great family Elateridse. This 

 power of springing into the air when placed on the back is effected 

 by bending back the head and thorax, thus bringing the prosternal 

 spine to and slightly above the front edge of a cavity in the meso- 

 sternum (Fig. 272, e), and at the same time raising the base of 

 elytra slightly above the surface upon which the beetle is resting; 

 then by suddenly relaxing the muscles the spine descends with 

 force into the. cavity, causing the base of elytra to strike violently 

 against the supporting surface, and by their elasticity the whole 

 body is propelled upwards. Td bring about the motion in the 

 manner indicated there must be n loose articulation, so as to give 

 free movement between the pro- and i)iesi;sternum, and this char- 

 acter is a prominent one in the majority of the genera of Elateridas. 

 The hind angles of tlic thorax are prolonged backward into a point 

 so as to embrace the base of the elytra, and as the bases of the tho- 

 rax and elytra slope downwards toward each 

 other, a slight separation between them is suffi- 

 cient to permit the freedom of motion necessary 

 to the upward movement. 



The great majority of Elateridaj are small or 

 medium in size ; elongate in form, tapering more 

 or less toward each end; dull brown or blackish 

 in color and have the surface clothed with a 

 fine pubescence. They occur beneath bark, logs 

 and stones, or on the foliage of various plants, 

 most commonly in dry upland localities. The 

 word "Elatcr" means literally a "driver or 

 hurler, " and refers to the elastic power of 

 motion possessed by these beetles. 



The principal distinguishing characters of 

 the family are the 11-jointed, more or less ser- 

 rate (rarely flabellate or pectinate) antennae, 



Fig. 272. 



a, antenna in repose; 



b, antennal groove; 



c, tarsal groove; 



d, prosternal spine; 



e, niesosternal cavity; 

 /, metastemum ; 



0, hind coxal plates. 

 (Original.) 



