THE INSECT WORLD. 



199 



beetles belonging to this series. None of them are in any way 

 injurious. 



The exception in food habits in this family is found in the 

 genus Trox, containing oblong, very convex species, with rough, 

 tuberculate or pitted wing-covers, and a deeply furrowed thorax. 

 They are usually more or less incrusted with dirt, are found 

 feeding under old skins, bones, or hoofs, and are, as scavengers, 

 at least innoxious. 



The more typical ' ' leaf-chafers' ' are of diverse forms, often 

 common and economically important. Among the first we reach 



Fig. 188. 



Rose-chafer, Macrodactylus subspinosus. — a, beetle ; b, head and thorax, in outline, from 

 side ; ^ to^, structural details. 



the genus Macrodactylus, of which the "rose-chafer," or 

 "rose-bug" is a member. This appears in June at about the 

 time roses and grapes come into blossom, and eats their flowers 

 in preference to anything else. 



Occasionally, for a series of years, the insects appear in ever- 

 increasing abundance, until the swarms are so great that they 

 ruin not only vineyards but orchards and gardens, eating almost 

 every kind of fruit and flower. In the presence of such swarms 

 we are almost helpless, and insecticides are of no possible use. 

 No contact poison kills them, and the arsenites or other stomach 



