184 LEAF-MINING INSECTS 



fire perhaps as little modified as any larvae of leaf-mining 

 insects. 



The eggs of nearly all of the leaf-mining beetles, except 

 Curculionidae are laid upon the surface of the leaf. In 

 several cases they are coated and protected with excrement. 

 The eggs of the weevil leaf -miners are laid in the leaf tissue, 

 the holes for them being first excavated by the beak of the 

 females. 



Many of the Chrysomelid grubs have the habit of desert- 

 ing a mine in one leaf to migrate to another which they enter 

 at a new place. The majority of them are active in the 

 spring and early summer. The mines which they form are 

 in many cases rather puffed or blistered. 



With the exception of the few very generalized Chryso- 

 melid larvae the beetle miners pupate in the mine and emerge 

 from the leaf as adults. Some of the weevils have the 

 rather distinctive habit of spinning in their mines a silken 

 cocoon for pupation. 



The adult beetles from these respective groups of mining 

 grubs can be easily distinguished. The weevils will be 

 recognized at once on account of having the head produced 

 into a beak or snout. The Buprestids may be separated 

 by their rather bronzed and metallic appearance and by the 

 presence of grooves near the margin of the underside of the 

 thorax for receiving the infolded antennae. The Hispid 

 beetles are wedge-shaped with the hinder end broad and 

 truncate. The surface is usually strongly pitted and reticu- 

 lated in our American species and some exotic ones are even 

 spiny. The front of the head is flexed so that the mouth 

 is inferior. The flea beetles have a smooth often shining 

 surface and a regular oval form. Their posterior thighs 

 or femora are greatly thickened for jumping. 



The relation of the leaf-mining habit to other habits in 

 these various families is at first not very clear. Its existence 

 in the Buprestidae where most of the species bore in the wood 



