THE EVANIID^. 319 



are thought by many entomologists not to be indigenous, but 

 to have been brought over by vessels, and to have acclimatised 

 themselves. 



In these insects the thorax is enormously large, and the 

 abdomen is curiously small, scarcely larger, in fact, than one 

 of the hind-legs. It is very slender, and attached to the upper 

 part of the thorax by a slight footstalk, just below the inser- 

 tion of the wings. In some species, the abdomen is barely 

 half the size of one of the hind legs, and bears about the same 

 relative proportion to the thorax that a comma (such as this ,) 

 bears to the capital letter 0. In fact, the creature seems to 

 be all legs and wings, without any nutritive apparatus. 



All the Evaniidoe are small, but we may gain some idea of 

 their remarkable construction if we take the head, thorax, 

 legs, and wings of a wasp, remove the abdomen altogether, 

 and substitute the corresponding part of a gnat, stuck on 

 the upper part of the thorax, just at the base of the wings. 

 Only, to make the resemblance clearer, we must make the 

 hind legs nearly twice as long, and flatten the tibiae into trian- 

 gular plates. The Evaniidae are parasitic in their nature, but 

 their economy is not yet thoroughly known. 



