202 LEAF-MINING INSECTS 



they feed upon the leaves, perforating thinner ones and 

 digging pits into thicker ones. In the winter they conceal 

 themselves in dry places under stones, in tufts of grass and 

 moss or in the chinks of walls. They lay their eggs in the 

 spring upon the leaves of the plants which serve them for 

 food. Harris in "Insects Injurious to Vegetation" says of 

 their larval habits: 



The larvae or young of the smaller kinds burrow into the leaves 

 and eat the soft pulpy substance under the skin, forming therein 

 little winding passages in which they finally complete their trans- 

 formations. Hence the plants suffer as much from the depreda- 

 tions of the larvae as from the beetles. The mining larvae are 

 little slender grubs tapering toward each end and provided with 

 six legs. They arrive at maturity, turn to pupae and then to 

 beetles in a few weeks. Hence there is a constant succession of 

 these insects in their various states throughout the summer. 



None of the larvae are greatly specialized for mining. 

 All are more or less cylindrical tapering at the extremities 

 and supplied with well developed thoracic legs. 



Dibolia 



The plantain flea beetle, D. borealis, attacks the broad- 

 leaved Plantago major, and fills its leaves in early summer 

 with irregular linear mines, that run for the most part 

 lengthwise of the leaf, and that are often lobed and branched 

 and anastamosing. The miner is a minute yellow larva 

 having a blackish head and a longitudinally divided pro- 

 thoracic shield. It is but little depressed; and as the leaf 

 is thin it lifts the epidermis and leaves it a little elevated 

 like the roof of a mole-run in the soil. (See fig. 57, 3. J 



The yellow eggs are laid on the upper surface of the leaves 

 in the spring in small holes that are made by the female with 

 her jaws for their reception. They are partially covered 

 with blackish excrement. The larvae on hatching at once 



