4 BULLETIN 435, U. S. DEPARTMENT OF AGRICULTURE. 



side (PL I, fig. 2) and, crawling to another leaf, repeats the folding 

 and sewing operation. 



During the season a single larva will thus destroy several leaves, 

 and when the insect is present in sufficient numbers, extensive 

 defoliation may result. 



Felt, in discussing the habits of the apple leaf sewer or "folder," 

 as he designate3 it, states that the common name "apple leaf folder " 

 exactly describes the work of the caterpillar, since the presence of the 

 dark yellowish-green, black-marked caterpillars is most easily recog- 

 nized by the apposed halves of infested leaves, their edges being 

 held together by strands of silk. 



From observations made in the spring of 1915 it developed that 

 the larva of the apple leaf-sewer does not begin to sew up the leaf 

 immediately on leaving the egg, as stated by Riley, Felt, Fletcher, 

 and others. This would seem an impossible task for the newly 

 hatched larva because of its minute size. 



DESCRIPTION OF STAGES. 



THE EGG. 



As far as can be ascertained, no description of the egg has been 

 made in the literature of the apple leaf-sewer. This is probably 

 due to the fact that the egg is minute, inconspicuous, and difficult 



to detect. Except in color, it 

 bears a striking resemblance to 

 the egg of the codling moth, be- 

 ing a flat, somewhat oval-shaped 

 object with a raised circumfer- 

 ence or flange and a shallow de- 

 pression in the center (fig. 4, b). 

 The eggs are about the size of 

 pinheads, and are fairly uniform, 

 averaging about 0.8 mm. in 

 length and 0.6 mm. in width. 

 The surface is covered with a 

 network of ridges which are 

 closer together and more regular 

 toward the central portion than 

 around the edges. When first 

 deposited the eggs are the color 

 of the leaf and it is only in reflected light that they can be detected. 

 In 48 hours the color changes to a deep yellow. Later the embryo 

 is indicated by the raised outer edge becoming darker in color, and 

 shortly before hatching the larva is plainly visible, bent like a U 

 around the central depression. The eggs are always securely glued 



Fig. 4.— The apple leaf-sewer: a, Apple leaf, with posi- 

 tion of egg indicated ; 6, egg on portion of leaf, greatly 

 enlarged. (Original.) 



