290 J our7ial of Agricultural Research voi. vi, no. s 



York, and Brunn (i) reported it from Ithaca, N. Y. Forbes (4, p. 57) 

 reported it from Illinois, New York, Colorado, Kentucky, Michigan, and 

 Massachusetts; and Jar\ds (5, p. 49) reported it as being common in 

 Connecticut. Dietz (3) reported it from the Middle and Northern States 

 of the Atlantic slope, though he confused species. In a recent attempt 

 to determine its present distribution the writer has been able to get defi- 

 nite records from but one additional State, Ohio. It is probable that it 

 is found from the Atlantic States to Colorado, but being so small and 

 inconspicuous, except when abundant, fruit growers and entomologists 

 have overlooked the insect and its work. 



LIFE HISTORY OF THE MINER 



The writer has not been able to find any report of the complete life 

 history of the pest. Such records as are available deal with the insect 

 and its development and work in the summer or more often for a short 

 period in the late fall. In some cases very careful data have been re- 

 corded, but many of the records and descriptions are decidedly at fault. 

 The following records for the insect in Missouri have been collected since 

 the summer of 191 1 and include new data on the life history, develop- 

 ment, and habits of the pest. 



EGG 



The ^gg is extremely small, slightly oblong, varying from 0.254 to 0.4 

 mm. in length and from 0.18 to 0.29 mm. in breadth, only slightly ele- 

 vated and firmly cemented invariably to the lower surface of the leaf. 

 (PI. XXXIII, fig. 3.) It is so small that it can scarcely be detected with 

 a hand lens, and the writer has failed to find the unhatched eggs on foli- 

 age, though many have been collected and studied soon after hatching, 

 when the young caterpillar had just begun to start its mine. The adults 

 have refused to lay eggs in captivity in small vials; therefore, these rec- 

 ords are for the freshly hatched eggs. 



THE LARVA 



On hatching, the larva is footless and resembles a microscopic flat- 

 headed borer. It always seems to break through the part of the shell 

 which is cemented to the leaf and enters the tissue of the leaf at once. 

 The freshly hatched caterpillar is less than a millimeter in length. It 

 grows rapidly and when mature is about 6 mm. in length. In its de- 

 velopment it passes through four distinct larval stages. There is con- 

 siderable variation in size, but the following measurements are the 

 average of many specimens. 



In the first stage the caterpillar is pale, with a slight yellowish tinge 

 to the head. The head and thorax are enlarged and it is footless. It 

 molts when it is yet less than 2 mm. in length, and the head capsule is 

 about 0.18 mm. in breadth. (PI. XXXIII, fig. 4.) 



