526 Journal of Agricultural Research voi. v, no. 12 



in size, especially in its breadth, the mine becomes light brown, while 

 the edges incline to a darker shade. Observed from beneath, the only 

 visible indication of the initial activities of the insect is a small oval 

 spot, which marks the original cavity constructed by the adult for the 

 reception of the &gg, and this contains in addition to the shriveled egg 

 membrane accumulations of frass from the early feeding operations of 

 the larva. Later, the underside of the tunnel also becomes brown, with 

 the exposed epidermis wrinkled, but, in general, the destructive work of 

 the insect is not so apparent on the lower as on the upper surface of the 

 leaf. 



There is a fairly definite relationship between the size of the mine and 

 the age of the larva with respect to the different instars. In general, 

 mines under 5 mm. long and 2 mm. at their greatest width contain larvae 

 in the first instar; mines that are 5 by 2 mm. to 12 by 4 mm. contain 

 larvae in the second instar; mines that are 8 by 5 mm. to 8 by 6 mm. con- 

 tain larvae of the third instar; mines that are 18 by 6 mm. to 28 by 8 mm. 

 contain larvae of the fourth instar; and mines of greater dimensions than 

 the foregoing are occupied by larvae of the fifth instar. 



PUPATION 



Upon reaching maturity the larvae make a hole in the tissues forming 

 the mine, usually the upper epidermis, which forms the roof. From the 

 opening they make their escape to the edge of the leaf, when they drop 

 to the ground. During 191 2 the larvae began to leave the foliage on June 

 7, and by June 10 it was estimated that 50 per cent of the insects had 

 abandoned their mines. On June 18 it was difficult to find a specimen on 

 the tree, while June 22 was the latest date that any of the insects were 

 seen on the leaves. Upon reaching the ground they bury themselves 

 several inches deep in the soil and construct an earthen cell. The 

 cocoon, which is oval in shape, consists of particles of earth glued together 

 and lined with a cement which renders it impervious to water and strong 

 enough to resist considerable pressure without crushing. The insect 

 passes the winter in the larval stage. However, the pupa begins to form 

 in the fall. Specimens obtained during October showed the developing 

 compound eyes and ocelli, while of examples secured the following April 

 the adult characters of the head could be plainly seen through the skin, 

 and their bodies were decidedly humped. One of these specimens which 

 was kept in a cool room transformed to a pupa on or before April 23. 

 Others obtained from an orchard on May 2, 191 3, were all in the pupal 

 stage, and one female pupa was partly colored. 



NATURAL ENEMIES OF SAWFLY LEAF MINER' 

 A common enemy of the sawfly leaf miner is the chalcidid Trichogramma 

 minutum Riley, which is an egg parasite. During the five years that 



' Through the courtesy of Dr. L. O. Howard, the identifications of the parasites were made by Messrs. 

 A. A. Girault and A. S. Rohwer, of the United States Bureau of Entomology. 



