88 LEAF-MINING INSECTS 



summer generation pupation takes place a few days before 

 the emergence of the adult. In the hibernating generation 

 pupation may be delayed until spring. 



The adult. The moths are among the smallest of all the 

 lepidoptera, some of them expanding scarcely 3 mm. (J inch). 

 The two pairs of wings are similar in shape, elongate, ovate 

 and pointed. Some of the species are dull brownish or drab, 

 while others are ornamented with shining metallic spots or 

 bars. They are of a retiring habit and are not often met on 

 the wing. 



Typical of this great genus of micros is the plum leaf- 

 miner A r . sling erlandella. 1 Crosby (1911) has written the 

 best account of the habits of this species, and from his 

 bulletin we quote the following : 



The plum leaf-miner is a new fruit pest and is doubtless a 

 native American insect. The larva first eats a narrow linear mine 

 an inch or less in length, then widens the mine so as to produce an 

 irregular, more or less ovate blotch about one-half inch long. 

 The part of the leaf so injured turns brownish and dies. From 

 three to twelve mines are often found in a single leaf. The trees 

 become partially defoliated and the fruit may fall prematurely. 



The eggs are attached to the under surface of the leaf, usually 

 at the forks of the more prominent veins. The egg is about 0.3 

 mm. long by 0.2 mm. wide, oval in outline, flattened where at- 

 tached to the leaf and dome-shaped in profile. The green of the 

 leaf shows through the transparent eggshell, making it a difficult 

 object to find. The eggs are most easily located by holding a leaf 

 at an angle in the sun so that the light will strike it obliquely, when 

 they will be seen as minute glistening dots. 



In hatching, the larva eats its way out of the eggshell on the 

 underside next to the leaf, and enters the leaf directly without 

 coming out on the surface. This is a point of great practical 

 importance, as showing the futility of attempting to kill the larvae 

 with an arsenical spray. When full grown the larva is about one 



1 Named in honor of the late Professor Mark Vernon Slingerland, who 

 first studied it in New York State. 



