86 
Journal of Agricultural Research 
Vol. I, No. i 
The larvae injure the foliage of the plant by burrowing between the 
membranes of the leaf and devouring the parenchyma. 
The injury takes the form of a serpentine “mine” which encircles the 
leaf, gradually widening as the larva increases in size. 
Leaves of white clover and frequently of young alfalfa often have the 
entire cellular tissue devoured, leaving only the two membranes. 
There is usually only one larva present in each leaf. 
The injury from this insect is greatest in the Southwest, where the dis¬ 
colored leaves, which in severe cases become brown, are sometimes present 
in sufficient numbers to lower the quality and grade of the hay. 
The injured leaves can be found in the fields from May until Novem¬ 
ber, the larvae continuing to feed until killed by frosts. In Florida the 
larvae continue feeding throughout the winter. 
The insect hibernates in the puparia beneath the surface of the soil at 
the base of the plants. 
There are five or six generations in latitude 41 °, the number varying 
with the length of the growing season. 
The generations overlap to such an extent that all stages can be found 
in the fields during most of the season. 
During the period of highest temperature in summer the larvae are 
found usually infesting plants protected from the direct rays of the sun. 
During this period in the arid Southwest the insect almost completely 
disappears from the fields, reappearing in September. 
The eggs are deposited in the leaf tissue and inserted in punctures 
identical with those made by the adult in feeding. The egg stage during 
June is 4 da}^s. 
The larvae feed continuously day and night and confine their work to 
a single leaf. The larval period during June is 4 days. 
In the Eastern States pupation occurs entirely in the soil. It takes 
place commonly in the larval chambers in the leaf in the arid Western 
States. The pupal period during June is 10 days. 
The average period of the complete life cycle is 23 days. 
Besides alfalfa the following field crops are subject to attack: Clover, 
cowpeas, rape, and cotton. 
A few nearly related and very similar leaf-miners are known to attack 
timothy, wheat, oats, and grasses. When these crops are affected, the 
mine usually extends the entire width of the leaf, and may kill the plant 
if it is very young. 
Numerous parasitic insects attack and consume the larvae and pupae 
within their mines. These are highly efficient and serve to keep the 
insect in control. 
The efficiency of the parasites decreases upon the approach of cool 
weather. 
Many of these parasites are functional in the control of more than one 
species of leaf-miner, and are very widely distributed. 
