258 COLEOPTERA 



CHAP. 



membrane in which it is placed appears to be elastic, Although 

 the mechanics of the act of leaping are still obscure, yet certain 

 points are clear ; the prosternal process possesses a projection, or 

 notch, on its upper surface near the tip ; as a preliminary to 

 leaping, this projection catches against the edge of the me so- 

 sternal cavity, and as long as this position is maintained the 

 Insect is quiescent ; suddenly, however, the projection slips over 

 the catch, and the prosternal process is driven with force and 

 rapidity into the mesosternal cavity pressing against the front 

 wall thereof, and so giving rise to the leap. 



Several larvae are well known ; indeed the " wire-worms " 

 that are sometimes so abundant in cultivated places are larvae 

 of Elateridae. In this instar the form is usually elongate and 

 nearly cylindrical ; the thoracic segments differ but little from 

 the others except that they bear rather short legs ; the skin 

 is rather hard, and usually bears punctuation or sculpture ; 

 the body frequently terminates in a very hard process, of 

 irregular shape and bearing peculiar sculpture on its upper 

 surface, while beneath it the prominent anal orifice is placed : this 

 is sometimes furnished with hooks, the function of which has 

 not yet been observed. The majority of these larvae live in 

 decaying wood, but some are found in the earth ; as a rule the 

 growth is extremely slow, and the life of the larva may extend 

 over two or more years. Some obscurity has prevailed as to their 

 food ; it is now considered to be chiefly flesh, though some species 

 probably attack decaying roots ; and it is understood that wire- 

 worms destroy the living roots, or underground stems, of the crops 

 they damage. Various kinds of Myriapods (see Vol. V. p. 29) are 

 often called "wire-worm," but they may be recognised by possessing 

 more than six legs. The larvae of the genus Cardiophorus are very 

 different, being remarkably elongate without the peculiar terminal 

 structure, but apparently composed of twenty-three segments. 



The genus Pyrophorus includes some of the most remarkable 

 of light-giving Insects. There are upwards of 100 species, 

 exhibiting much diversity as to the luminous organs ; some 

 are not luminous at all ; but all are peculiar to the New World, 

 with the exception that there may possibly be luminous species, 

 allied to the American forms, in the Fiji Islands and the New 

 Hebrides. In the tropics of America the Pyrophorus, or Cucujos, 

 form one of the most remarkable of the natural phenomena. 



