522 
Journal of Agricultural Research 
Vol. V, No. 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 the 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 
EGG 
The egg is elliptical in shape, but is not entirely symmetrical in its outline, as 
one side shows a greater curvature than the other. It is, when removed from sur¬ 
rounding plant tissues, circular in cross section, but in its normal position in the 
leaf structure it is much flattened, owing 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 carefully examined for all 
insect remains, when the head molts were collected and measured 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 tapers 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 rounded 
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 diort 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. 
