FIELD BOOK OF INSECTS 



narrow, as compared with the abdomen. They occur on 

 the ground under things, usually in damp places. Many 

 Carabidae, when disturbed, give off a defensive fluid from 

 a gland at the end of the abdomen but species of Brachi- 

 nus do it with a distinct "pop." For this reason, they 

 are called Bombardier Beetles. The discharged fluid 

 is either volatile or it is shot out in a fine spray, so that 

 it looks like smoke. 



Under stones and logs in damp places 

 Chlaenius . . 



are often found Carabidae with a pro- 

 nounced musky odor and brilliant, bronzed or green, 

 backs, very finely clothed with short hair. C. sericeus 

 is all green, .6 in. long, with yellow legs, while other species 

 of the genus are smaller and variously colored. 



Plate ' LXXII shows one of the largest 

 Harpalus , 



and commonest species, cahginosus. It 



is black with reddish-brown antennae and tarsi. H. 

 pennsylvanicus is also common and is, superficially 

 much like caliginosus except that it is rarely more than 

 .7 in. long. For that matter, there are a dozen or more 

 species of Harpalus, in almost any region, for which our 

 figure would do except as to size. It might also pass for 

 related genera such as Selenophorus, Stenolophus, and 

 Anisodactylus. Unlike their relatives, some species of 

 Harpalus are said to feed, when adult, largely on seeds. 

 Harpalus viridi&neus, with shining, greenish-bronze 

 back, is common under boards in farmyards. 



Agonoderus pallipes (Plate LXXIII) is a small relative 

 of Harpalus that often enters houses at night, attracted 

 by the lights. 



The next three families are aquatic (see also Hydrophili- 

 dae), although the adults may leave the water to seek 

 mates and new abiding places. The compound eyes of 

 the Gyrinidae (series Polymorpha) are divided so that they 

 seem to have four such eyes; the abdomen has seven 

 segments; the middle and hind legs form short broad pad- 

 dles; the antennae are short. The eyes of Haliplidae and 

 Dytiscidae are not divided; the antennae are thread-like; 



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