700 FAMILY XXXVri. ELATEIUD/E. 



which are inserted in grooves on, or under the margin of the front; 

 the frequently retracted, sometimes advanced head ; elytra covering 

 the abdomen, which has five free ventral segments; prosternum 

 long, usually lobed in front, prolonged behind into an acute spine 

 moving in the mesosternum, the latter short, with a cavity in the 

 middle for the reception of the prosternal spine (Fig. 272, d and 

 e) ; front coxae small rounded, v^^ithout trochantins, the cavities 

 open behind ; middle coxse small, rounded with distinct trochantins ; 

 hind coxaa transverse, oblique, contiguous, dilated (except rarely) 

 into a plate covering in part or entirely the thighs (Fig. 272, g) ; 

 tarsi 5-jointed, simple or lobed beneath ; claws simple, toothed or 

 pectinated. 



All the species of Blateridas are vegetable feeders, and are hence 

 to be classed as injurious, though many -of them feed upon the 

 juices of rotten wood. The larvte are long, narrow, worm-like crea- 

 tures, very even in width and with a 

 hard, brownish or yellowish-white 

 Fig. 273. (After Forbes.) body covcriug. (Fig. 273.) They 



are commonly known as "wire-worms," and those species which live 

 in the ground feed upon seeds and the roots of grasses and grain, 

 and often do much damage, especially to sprouting corn and other 

 cereal crops. Working as they do beneath the surface of the 

 ground, they are exceedingly difficult to destroy. In many of the 

 more injurious species the larva requires several years to complete 

 its growth, and when full grown usually changes in late summer 

 into a pupa in a little cell in the ground. Either the pupa or adult 

 Ijeetle remains in this cell until spring, and it has been found that 

 much can be done toward'; keeping them in check by fall plowing, 

 which breaks up these cells and exposes the pujne or young adults 

 to the rigors of winter. 



About 7,000 species of Ela1crid;v ai-e known, more than .')60 

 being listed from the United Slates. 



On account of the large size of the family and the strong general 

 resemblance of many of the species, their classification is very diffi- 

 cult, especially to beginners. The genera belonging to the principal 

 subfamily, the Elaterinaj, have, for the most part, been treated in 

 special s.^iiopses or monographs, which will be mentioned under the 

 proper generic headings. The principal works dealing with the 

 family or the other subfamilies of the North American forms are as 

 follows : 



Lrdonte. — "Synoi)sis of the Eucnemides of Temperate North 

 America," in Proc. Phil. Acad. Nat. Sci., VI, 1852, 45-49. 



