522 Journal of Agricultural Research voi. v, xo. 12 



back, with correspondingly ill effects on the maturing crop of fruit. In 

 years when the production of new growth is more rapid the damage 

 caused by t he sawfly leaf miner is of much less importance, as the large 

 leaf surface under the circumstances is sufficient for the needs of the 

 plant, and the loss of affected foliage does not result in an important 

 reduction in leaf area. 



The hawthorns are more subject to severe attacks than the cherry, 

 and during some seasons plants may be observed on which there is 

 hardly a leaf that does not show injury. Notwithstanding the par- 

 tiality of the sawfly leaf miner for this plant, hawthorns seem able to 

 withstand considerable destruction of foliage without marked external 

 evidences of the weakening of the tree. As shown in Plate LI, figure 2, 

 the attractiveness of the plants as ornamental shrubs may be seriously 

 marred. 



DESCRIPTION OF LIFE STAGES OF SAWFLY LEAF MINER 



The egg is elliptical in shape, but is not entirely symmetrical in its outline, as 

 one side shows a greater ciirvature than the other. It is, when removed from sur- 

 roimding plant tissues, circular in cross section, but in its normal position in the 

 leaf structure it is much flattened, o^ving to pressure. The chorion is a thin, white, 

 shining, flexible membrane. The measurements of eggs when not compressed are: 

 Length, 0.5 to 0.7 mm.; diameter, 0.28 to 0.36 mm. 



LARVA 



To determine the number of instars, the mines were careftilly examined for all 

 insect remains, when the head molts were collected and measiired as to width. The 

 body remnants from some of the molts in first larval instars were occasionally miss- 

 ing, having probably been eaten, but in very few cases were the head structures 

 not in good condition for examination. The width of the head is fairly constant 

 for the first larval instar, but in the more advanced stages there is considerable vari- 

 ation. On the basis of head measurements it appears that the larva normally molts 

 five times in its mine. It finally enters the ground and molts again in transforming 

 to a pupa. 



The first five instars have the same general form and differ one from the other 

 principally in size. The body is broadest at the first and second thoracic segments 

 and gradually tapere toward the rear. The thoracic legs are short and conical and 

 are composed of five segments, which include the thick basal and the small hooked 

 terminal structures. All the abdominal segments except the last bear short rotmded 

 prolegs on the ventral side. The head is horizontal in the early stages, but slopes 

 downward slightly in later instars. It is broad and flat, rounded on the sides, and 

 obtuse in front. On the dorsal side it bears four longitudinal sutures. The outer 

 pair run back from the ends of the clypeus and divide the head into three almost 

 equal sections. The inner pair extend halfway across the middle section, dividing it 

 into three equal areas. The eyes are wanting. The antennae are very short and are 

 apparently composed of three segments. The maxillary palpi are large and protrude 

 from beneath the head. The labial palpi are very small. The mandibles are short 

 and thick, deeply hollowed on the inner side, and do not protrude beyond the end 

 of the broadly notched labrum. 



