Apr. 15,1914 
Corn-Leaf Blotch Miner 
21 
yellow, most distinct on knee joints; mid tibia with the posterior bristles distinct. 
Wings clear, slightly grayish on anterior half; venation as in Plate III, figure 1, A; 
halteres yellow, the knob whitish. Length, 3 to 4 mm. 
Originally described from the District of Columbia (Osten-Sacken). 
LIFE HISTORY OF AGROMYZA PARVICORNIS 
OVIPOSITION 
The act of oviposition has never been observed by the author, although 
the females have often been seen making feeding punctures which are 
apparently the same as egg punctures. 
The eggs, which have been observed in the leaves repeatedly, may be 
deposited either from the upper or lower surface. The females always 
choose the tip of the leaf in small plants when ovipositing in the field, but 
in large plants the eggs may be placed 
at any point on the leaf. In confine¬ 
ment they seek the tips of the small 
leaves also, but as there is necessarily a 
small amount of leaf surface in a small 
cage, there are often as many as 15 
eggs deposited in one leaf at different 
points. The eggs are inserted with the 
long axis parallel to the veins of the 
leaf. Figure 2, a, represents the eggs 
in situ and also greatly enlarged. 
In making the puncture the fly forces 
the point of her abdomen downward, 
rearing the anterior portion of her 
body slightly, and touches the tip of 
the abdomen to the leaf, whereupon 
the small lancets, which apparently 
make up the ovipositor, are put in motion. The lancets appear to 
slide past each other, with their cutting edge in the plant tissues, thus 
acting somewhat like a saw. They are forced down between the two 
surfaces of the leaf and a strip of the epidermis about 0.3 mm. in width 
and about 0.9 mm. long is pushed back; the egg is probably inserted 
then, and this flap is in some way brought back over the egg and fastened 
down, probably with a mucilaginous substance. Sometimes it appears 
as though both ends of the egg were covered, although eggs are often 
seen to be only partly covered. These eggs can be readily detected with 
the naked eye when only a few feet away, as they show as milky white 
spots against the green background. 
When only feeding, the female, after making the puncture, steps back¬ 
ward a few paces, inserts her proboscis into the puncture, and sucks the 
juices. The male has never been observed feeding at these punctures. 
The feeding punctures are very numerous, sometimes small leaves being 
c 
Fig. 5. —Agromyza parvicornis, the corn-leaf 
blotch miner: Puparium; a, dorsal view; 
&, ventral view; c, view of posterior ex¬ 
tremity. Much enlarged. (Original.) 
