COLEOPTERA 



479 



But the two families can be easily distinguished by the fact that in 

 the ground-beetles all the tarsi are five-jointed, while in the darkling 

 beetles the hind tarsi are only four-jointed; and the darkling 

 beetles do not run rapidly as do the ground-beetles. 



With the ground-beetles, the antennas are thread-like, tapering 

 gradually towards the tip, and each segment is of nearly uniform 

 thickness throughout its length ; the legs are fitted for running, and 

 the antennas are inserted between the base of the mandibles and the 

 eyes. Although most of the species are black, there are those that 

 are blue, green, or brown, and a few that are spotted. The wing- 

 covers are almost always ornamented with longitudinal ridges and 

 rows of punctures. 



Most members of this family are predacious, feeding upon other 

 insects, which they spring upon or capture by chase. A few species 

 use vegetable food ; but their depredations are rarely of economic 

 importance. As there are more than two thousand described North 

 American species, and as many of the species are very common, this 

 family may be considered the most important family of the pre- 

 dacious insects. 



The larv^ of ground-beetles are generally long, with the body of 

 nearly equal breadth throughout (Fig. 558). 

 They have sharp projecting mandibles; and 

 the caudal end of the body is usually furnished 

 with a pair of conical bristly appendages. They y'ip. 



live in the same obscure situations as the adult 

 insects, but are more shy, and are consequently less frequently seen. 

 Like the adults, they are predacious. 



Among the more common ground-beetles are the following. 

 The searcher, Calosoma scrutator. — This is one of the larger and 

 more beautiful of our ground-beetles ; it has 

 green or violet wing-covers margined with 

 reddish, and the rest of the body is marked 

 with violet-blue, gold, green, and copper 

 (Fig- 559)- This beetle and the two follow- 

 ing have been known to climb trees in search 

 of caterpillars. 



Calosoma sycophdnta, a common species 

 in Europe, has been introduced and success- 

 fully colonized in New England, as a means 

 of combating the gipsy-moth and the 

 brown-tail moth. This species is somewhat 

 smaller than the preceding, and lacks the 

 reddish band on the margins of the elytra. 

 The fiery hunter, Calosoma calidum, is 

 easily recognized by the rows of reddish or 

 copper-colored pits on the wing-covers (Fig. 



560). 



The bombardier-beetles, Brachinus. — There are many species of 

 beetles that have at the hind end of the body little sacs in which 



558. 



