Apr. a, 1917 
Wheat-Sheath Miner 
21 
mining up and down the leaf sheath and sometimes girdling the stem 
without completely cutting it off. Whether it girdles the stem or not, 
the injuries caused by mining in the sheath appear to be sufficient to 
kill the stalk. 
Some of the farmers who were interviewed in regard to the damage 
done by this insect estimated that their yields of winter wheat had been 
cut down at least 25 per cent in the season of 1915. Though hew shoots 
often spring up from the lower nodes after the central stalk is killed, 
these are not as strong and do not bear as large or as full heads of grain 
as the normal stalk. 
A field of spring wheat was visited in 1916, in which by actual count 
95 per cent of the plants showed injury by this insect. Some of these 
plants had only one culm injured, while others had lost two or three. An 
adjoining field of oats was found to have 12 per cent of its plants infested. 
There is a slight amount of injury done to the plants, just before 
blossoming, by the second brood of larvae. This injury is only to the 
leaves and probably has little or no effect on the yield, as the central stalk 
does not seem to be injured. 
To what extent the larvae injure winter wheat in the fall has not yet 
been ascertained. Farmers have stated that they have seen the injury 
in winter wheat, but it has been impossible to make an investigation of 
this statement because very little winter wheat has been grown in the 
infested localities in the last two years. 
LIFE HISTORY AND HABITS OF THE MINER 
The study of the life history of the wheat-sheath miner was carried 
on in the insectary at Bozeman, with material collected in the vicinity 
of Arlee. Several plants containing eggs and larvae were collected at 
Arlee on June 7, 1915, and were brought in for the purpose of rearing a 
supply of adults and securing all the data possible regarding this species. 
Adults emerged in the insectary on July 11 and continued to emerge 
until July 24. These adults were kept alive for some time, and their 
habits were studied in various ways. The first flies to emerge were 
placed in lamp-chimney cages over seedling wheat plants. The females 
fed on the juices of the wheat plants by making tiny incisions in the 
upper surface of the leaves and then lapping up the juices which exuded. 
One female fly caged over a wheat plant made 102 feeding punctures in 
24 hours. The males showed no inclination to feed on these juices; but 
when some wheat blossoms were placed in the cages they appeared to 
feed on the pollen, touching the anthers continually with the labella. 
The flies began feeding almost immediately on emerging, and one newly 
emerged female was seen to make three feeding punctures in five minutes. 
Copulation may take place any time after 24 hours from emergence, 
and this is followed by a preoviposition period of about three days. 
The oviposition period in the insectary was about 10 days, but is, with¬ 
out doubt, longer under natural conditions. 
