THE PEAE LEAF-WORM. 5 



changes to light brown and the wrinkles disappear as the body fills 

 out. After the second molt the average length is about 6 nun. The 

 head appears green and toward the end of the instar is lightly dotted 

 with small brown spots. The folds or wrinkles in the cuticle and 

 sutures appear as white stripes and spots. The length after the third 

 molt is 9.2 mm. While at first the larva is similar in appearance to 

 the preceding instar, the color later is bluish green with whitish 

 lateral and dorsal stripes, due to the folds of the skin. These whitish 

 stripes disappear at maturity, when the folds have become filled out. 

 By the time the larva has cast its first skin (on the average 5^ days 

 after hatching) it has eaten a hole with average diameter of 3.8 mm. 

 After the second molt (on the average 8^ days after hatching) it has 

 eaten out an area of about 12 mm. diameter. Four larvae were found 

 to have eaten during their larval existence 514, 241, 280, and 416 sq. 

 mm. of leaf, respectively, the first of these having consumed somewhat 

 more than one-fourth of an average-sized pear leaf (Bartlett). 



It was found that a considerable percentage of larvae died at the time 

 of their emergence because they were unable to cut their way through 

 the eggshell or through the leaf. Also during the first instar there 

 was considerable mortality due to imknown causes. During the 

 operation of molting numbers fall to the ground, because the larva 

 retains only a precarious foothold at this time and is easily shaken or 

 knocked off. 



Ihe width of a strip of leaf eaten by the larva during one of its 

 circular trips around the hole is equal to three-fourths the height of 

 its head. It eats as far as it can reach forward without advancing. 

 The head of the larva is always closely in contact with the leaf, filling 

 up the place of that portion eaten away, as does also its body, which 

 lies at full length along the edge of the hole (fig. 1, &). It is for this 

 reason that the edge of the loaf, defining the hole, appears to be an 

 uninterrupted line, and the larva, being almost the color of the leaf, 

 is not readily detected without close examination, but its presence 

 is made known by the characteristic circular holes that it cuts in the 

 leaves. In feeding the larva holds the posterior end of the body 

 either straight along the edge of the opening or curled about it, and 

 eats around and around the hole, which becomes gradually larger. 

 Where the larvae are numerous and two or more feed on the same leaf 

 they may soon consume it entirely, whereupon they migrate to other 

 leaves and commence feeding on the edges (fig. 1, a), as they are 

 imablc to oat througli. the flat surfaces. The larvae feeding along the 

 edges of tlio leaves on the lower part of tlio tree are mostly those 

 which drop down from above, being dislodged at the time of molting 

 or from s(;me other cause. Wliilo migrating along the loaf petioles 

 or the edges of the leaves the posterior part of the body is carried in 



