22 
Journal of Agricultural Research 
Vol. IX, No. i 
-The plants which were brought in from the field on June 7 yielded 
flies from July 11 to July 24. As there was no possibility of eggs being 
laid after June 7 in those particular plants, theoretically the last eggs 
laid produced flies that emerged on July 24. If all the flies completed 
their life cycle relatively in the same length of time, the eggs which 
produced the flies emerging on July 11 must have been laid 13 days 
earlier than June 7, or on May 25. . As the flies were plentiful on June 
7 and were still laying eggs, it is probable that the oviposition period 
lasts about three weeks, or from May 20 to June 10. 
The number of eggs laid by a single female was not ascertained, 
though six flies, caged over wheat plants, laid 96 eggs in 24 hours, which 
gives an average of 16 eggs per fly for that time. 
The egg-laying process is simple and takes from 7 to 12 seconds. The 
ovipositor is brought at right angles to the surface of the leaf, the upper 
epidermis is punctured, and the ovipositor is forced underneath it, 
toward the base of the leaf. A contraction of the abdomen forces the 
egg into the lower end of the puncture and the ovipositor is withdrawn, 
leaving the egg well protected under the epidermis. The feeding punc¬ 
tures are made in a similar manner, except that the leaf surface is scraped 
instead of the epidermis being punctured. 
The incubation period of the eggs is about six days under insectary 
conditions. Eggs were laid in wheat plants on two consecutive days, 
fresh plants being substituted each day. These eggs were watched, 
and six days later the first ones hatched and were followed by the rest 
the next day. 
Immediately on hatching from the egg the larva starts mining down 
the leaf toward the stalk, eventually ending in the leaf sheath, at the 
crown of the plant, or at the first node. On reaching the base of the 
leaf sheath the larva feeds up and down the sheath, and sometimes 
around the stalk. 
The length of the larval period is variable, as some of the larvae pu¬ 
pated at the end of 10 days, while some took as long as 20 days, depend¬ 
ing on weather conditions. Cool, wet weather seemed to delay pupation. 
Some of the larvae were removed from the leaf sheath and allowed to 
pupate in a tin box. Others were left in the plants to pupate normally. 
They did not leave the sheath, but .pupated either at the node or down 
close to the crown of the plant. None of them entered the soil or worked 
into the center of the stalk for pupation. 
The pupal period lasts about 25 days under insectary conditions. 
Larvae pupated in plants and in tin boxes on June 22 and emerged on 
July 16 and 17. What the variation in the length of the pupal period 
would be under varying weather conditions can not be estimated. As 
an indication that insectary conditions were parallel with natural condi¬ 
tions, wheat plants that were sent in from the field on the same date 
contained pupae from which flies were emerging. 
