180 LEAF-MINING INSECTS 



During the leaf-feeding period respiration is carried on 

 in the same way as in terrestrial lepidopterous larvae. Each 

 larva is working in a mine in the leaf but the entrance hole 

 and other openings which usually occur are sufficient to 

 provide the necessary air. When the larva deserts the leaf 

 and becomes a borer in the petiole new conditions are en- 

 countered and new provisions must be made. The burrow 

 in the petiole is filled with water and the larva is submerged. 

 When the length of the burrow increases to such an extent 

 that it is longer than the body of the larva which is making 

 it, the latter makes periodic trips to the surface where the 

 fresh air is drawn into the tracheal system in sufficient 

 quantity to allow a sojourn of several minutes under water 

 at the bottom of the burrow. When at the bottom of the 

 burrow the larva feeds (or in some cases merely rests) until 

 the need for air stimulates it to return to the surface. Then 

 it backs up to the top of the burrow, stopping when the 

 large pair of posterior spiracles is just pushed above the 

 surface film. It remains in that position until sufficient 

 air has been taken into the trachea to permit a return to 

 the bottom of the burrow again. This alternate sequence 

 of feeding and breathing goes on continuously so long as 

 the larve remains in the burrow. 



