ATTACKING THE ROOTS. 



239 



this is sometimes found another species (Hoplophora arctata 

 Riley) of a very curious form, reminding one of a mussel. 

 Fig. 246 represents this insect in different attitudes, highly 

 magnified. 



The gall-inhabiting type is very subject to the attacks of a 

 small two-winged fly, Diplosis grassator Fyles, which deposits 



FIG. 240. 



its eggs either in the gall or at its entrance, from which the 

 larva is soon produced. This, although destitute of legs, is 

 very active, and, groping about in the interior of the gall, 

 seizes on the young lice soon after they are hatched and sucks 

 them dry. It does not appear at first to attack the parent lice; 



FIG. 246. 



the tender progeny are more to its liking, and these are 

 produced in sufficient numbers to furnish it with a constant 

 supply of fresh food. In some instances one larva, in others 

 two are found in a single gall, and as they increase in size 

 they devour the lice very rapidly, and before changing to the 



