4 BULLETIN 438, U. S. DEPAETMENT OF AGRICULTURE. 



DESCRIPTION AND HABITS. 



THE EGG. 



The egg (fig. 1, a, h) appears on the surface of the leaf as a small 

 oval blister of a greenish color. It is reniform, slightly smaller at 

 one end, translucent greenish, and about 0.75 mm. in length and 0.50 

 mm. in maximum width. As the margins of the egg are more or less 

 covered by the edges of the ruptured epidermis of the leaf to which 

 it adheres, it is hard to remove the egg intact. This incised part of 

 the leaf epidermis appears as a narrow brownish area surrounding the 

 egg. On the lower surface of the leaf nothing is visible but a dark 

 spot, indicating the passage of the ovipositor. The egg is slightly 

 more oval than that of the pear slug {Caliroa cerasi L.), which it 

 greatly resembles. 



As miany as 20 eggs have been found in a single leaf, but ordinarily, 

 even upon a heavily infested tree, there are not more than three or 

 four and more often only one or two. 



Just before the egg hatches the whitish curved embryo with its 

 pink "eyespots" is visible through the shell. 



The manner of oviposition is described later in this section under 

 the heading of "The adult." 



THE LARVA. 



The larva emerges through the epidermis of the underside of the 

 leaf, apparently crawling out through the incision made by the adult 

 in depositing the egg. The newly hatched larva measures 1.3 mm. 

 to 1.7 mm. in length, and has an average width of 0.35 mm. As 

 soon as its head is free of the shell the larva begins to feed, cutting 

 a small round hole in the leaf. By the time the larva has fuUy 

 emerged, the hole or opening is large enough to permit the true 

 legs to grasp the edge, and as the hole is enlarged the whole body is 

 drawn in so that it lies in a curved position around the edge. The 

 true legs are gray, quite long, and are fitted for straddling the edge 

 of the leaf and not for walking over the surface. After a few hours 

 of feeding the color of the food begins to show through the body, and 

 the head and true legs become olive brown. There are seven pairs 

 of prolegs, which like the body are pale whitish or greenish-white. 



Molting takes place on the edge of the hole eaten out of the leaf 

 wherever the larva happens to be in the course of its feeding. The 

 larva crawls out of the old skin and soon resumes its feeding. The 

 skin usually adheres to the leaf for a time and is not eaten. After 

 the first molt the larva has a length of from 2 to 3 mm. Just after 

 molting the appearance is much as before, except that the head is 

 larger in proportion to the body and both it and the true legs are of a 

 lighter green than the body, which latter is considerably wrinkled 

 and slightly flattened, especially at the caudal end. Later the head 



