220 LEAF-MINING INSECTS 



are laid soon after emergence and the adults are short lived. 

 The eggs are laid in the axils of the lateral veins of the leaf, 

 the slits being cut apparently from the under side. At 

 first the eggs are hard to locate but they soon swell to a 

 diameter of about 0.5 mm. and are then very apparent 

 just within the lower epidermis. In about a week after 

 they become thus swollen the larvae may be seen curled 

 within the delicate egg membrane. Feeding and wriggling 

 they make their way into the tissue and up toward the upper 

 epidermis of the leaf where they feed with the venter upper- 

 most. They feed rapidly, extending the mine first between 

 the two veins proximal to the place of hatching, but later 

 increasing the area for half an inch or more along the mid- 

 rib and involving most of the space from the mid-rib to the 

 lateral border. 



In the first 5 instars the larvae are white with a pale brown 

 head. Beneath the 1st thoracic segment there is a black 

 oblong plate sometimes with a dot on either side and on each 

 of the succeeding segments except perhaps the last there is 

 a small black spot appropriately placed for shading the 

 nervous ganglia of the segments in the strong light upon 

 the upturned venter. The six thoracic legs are lateral in 

 position and not much used in progression. The prolegs 

 on abdominal segments 2, 3, 4, 5, 6, 7, 8 and 10 are poorly 

 developed. 



In the sixth instar the larvae are 7 mm. or more in length. 

 The head capsule is for the first time vertical to the plane 

 of the body. There age no spots on the white body in this 

 instar. The larvae now cease to mine but cut through the 

 upper epidermis, crawl to the edge of the leaf and fall to 

 the ground. The first larvae leave the leaf during the first 

 week of June and by the middle of June most of the mines 

 are empty. The larvae enter the soil to a depth of from 

 one to three inches and spin small cylindrical brown papery 

 cocoons. They remain the rest of the summer and the 



