12 LEAF-MINING INSECTS 



the prothorax for the attachment of the powerful muscles 

 there. It is the mid-dorsal margin of the head capsule that 

 is prolonged backward in sawfly larvae, the side margins, 

 in mining grubs and caterpillars. 



The pupa is, as always, the stage of making over from the 

 worm-like larva into the winged aerial adult insect. It is a 

 quiescent period of variable duration. It is passed in 

 seclusion either in the mine or in some shelter outside, or in 

 the ground. Cocoons are spun by the larvae of weevil 

 miners, sawfly miners, and by most mining caterpillars. 

 Each species has its own way of meeting its own needs. 



The adult insects of the four orders are in habits very 

 similar to the other members of their respective groups. On 

 reaching maturity their chief business is mating and egg- 

 laying. The females must seek out proper food plants and 

 deposit eggs in a fit manner to produce another generation. 



In the annual cycle there is always one brood per season, 

 and there may be several. The single-brooded forms may 

 be early, requiring soft, young leaves for their operations 

 (see Eriocrania, p. 76), or they may be late in season, 

 waiting until the leaf -tissues are full sized before entering 

 them (see Brachys, p. 190). The repeaters may have a 

 definite number of broods per season, two, three, four, or 

 even more, or the broods may so overlap in time as to be 

 indistinguishable. As with insects of other habits, the 

 number of broods may depend on climate and length of 

 season, there being more of them per year in southern 

 latitudes. 



THE MINES 



The dwelling places that these small miners excavate for 

 themselves within the leaves differ greatly in details, but 

 they may for convenience be grouped in a few categories. 



1. As to spread in the leaf, they are of two principal 

 kinds — linear and blotch. 



