526 
Journal of Agricultural Research 
Vol. V, No. 12 
in size, especially ip 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 egg, 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 br'own, 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 larvse 
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 1912 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, 1913, were all in the pupal 
stage, and one female pupa was partly colored. 
NATURAL* ENEMIES OF SAWFLY LEAF MINER 1 
A common enemy of the sawfly leaf miner is the chalcidid Trichogramma 
minntum Riley, which is an egg parasite. During the five years that 
1 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. 
