Dec. 20, J 9. 5 Cherry and Hawthorn Saw fly Leaf Miner 525 



counted 15 fully developed eggs. Another that had been out for two 

 days began to deposit eggs immediately when cherry leaves were intro- 

 duced into its cage. In the orchard eggs were first found during the year 

 1 91 3 on May 7; in that season adults were first observed on May 6, 

 although the insects may have been present on the trees for a day or two 

 before and escaped detection. During the first days of the oviposition 

 period one or sometimes two leaves in a cluster may show the presence 

 of eggs. The females seem to manifest a preference for leaves which are 

 first to appear and which are partly folded. The process of oviposition 

 requires only about a minute. Details of this operation proved difficult 

 to determine because of the extreme shyness of the females, which fly 

 quickly on the approach of any object. 



The lower surface of the egg lies in contact with the lower epidermis, 

 which has been cut free from the other tissues of the leaf so as to form a 

 small blister-like cavity or pocket. The egg is usually within i or 2 mm. 

 from the edge of the leaf; rarely on the extreme edge or more than 3 

 mm. from the margin. On the upper side at the edge of the cavity there 

 is usually a stoma, through which the ovipositor is probably thrust. An 

 examination of 91 eggs at random shows that they are more often de- 

 posited near the base of the leaf than the tip. About 70 per cent of 

 the eggs were in the area of the leaf from one-eighth to one-third the 

 distance from the base, 20 per cent near the middle, and about 10 per 

 cent occurred in the portion of the leaf toward the tip. From i to 5 

 eggs were observed on a single leaf, and the average for all observations 

 was 2.3 eggs per leaf. 



HATCHING .-^ND L-^RVAL ACTIVITIES 



During 191 3 young larvae were first observed on May 24 as the trees 

 were coming into full bloom, but judging from the sizes of some of the 

 mines it was evident that a few eggs had hatched one or two days earlier. 

 By May 27 the hatching period was practically completed. In the field 

 it proved difficult to determine the period of incubation, but eggs depos- 

 ited on cherry leaves in the insectary hatched in eight days from date of 

 oviposition. Under normal conditions incubation would probably extend 

 over a larger number of days. 



Upon hatching, the young larva works its way through the tissue of 

 the leaf until it reaches the upper epidermis. It usually mines toward 

 the distal end of the leaf, generally keeping close to the edge and feeding 

 with the ventral side in contact with the upper epidermis. When the 

 tip of the leaf has been reached the creature reverses its course, pro- 

 ceeding along the area adjoining the midrib; or if there is no interference 

 by another larva it may cross over the main rib and tunnel back along 

 the edge of the opposite half of the leaf. 



The mine, as viewed from above, during its first stages of development 

 is rather dark brown in color, which is accounted for in part by frass 

 along the edges of the roof of the tunnel. As the affected area increases 



