222 LEAF-MINING INSECTS 



and interesting account by P. J. Parrott and B. B. Fulton 

 (1900), from which the following is abstracted: 



The adult insect is a small sawfly which varies from 3 to 

 4 mm. in length. The body of the female is metallic black 

 with the prothorax rufous in color. The sawflies make 

 their appearance during early May at the time when the 

 first leaf clusters are unfolding and the blossom buds are 

 beginning to open. The eggs are laid singly through in- 

 cisions in the upper epidermis. The lower surface of the 

 egg usually lies in contact with the lower epidermis which 

 has been cut free from the other tissues so as to form a small 

 blister-like cavity or pocket. The egg is elliptical in shape 

 and when released from the pressure of the leaf and increased 

 to its greatest size, it is 5 to 7 mm. long and 0.28 to 

 0.36 mm. in diameter. The chorion is a thin, white, shining, 

 flexible membrane. The majority of the eggs are deposited 

 in the basal portion of the leaves. 



Hatching occurs during the middle or latter portion of 

 May. The young larvae work their way to the parenchyma 

 immediately beneath the epidermis of the upper surface of 

 the leaf and mine toward the distal end of the leaf gener- 

 ally keeping close to the lateral margin. The injury is first 

 indicated by a sinuous channel which finally swells out into 

 a large blister-like area. They are most conspicuous on the 

 upper surface of the leaves during early June. The larvae 

 are then making their maximum growth. 



By collecting and measuring moulted skins it was ascer- 

 tained that the larvae normally moult five times in the mine. 

 The first instars are very much alike, differing in the first 

 five chiefly in size. The body is widest at the first and 

 second thoracic segment and gradually tapers toward the 

 anal segment. The thoracic legs are short and conical and 

 of five segments, which include a thick, basal and a small 

 hooked terminal structure. All the abdominal segments 

 except the last bear short, rounded prolegs on the ventral 



