20 
Journal of Agricultural Research voi. ix, no. i 
segment. When not protruded, the chitinous process is drawn up into the body, 
sheathing the penis within the ventral portion of the fifth segment. 
The size of the female is the same as that of the male, and in general description 
the two sexes are alike. Abdomen less tapering, six segments, a seventh segment 
sometimes visible when the ovipositor is protruded. Ovipositor retractile, tubular, 
with a hard, chitinous edge. Posterior segment not cleft ventrally. 
NATURE AND EXTENT OF INJURY 
A field of wheat infested with the wheat-sheath miner may not appear 
to be greatly injured. Unless the field is badly infested the grain has a 
healthy color and ap¬ 
pears to be strong. A 
badly infested field ap¬ 
pears slightly off color 
and may show areas 
which look decidedly 
unhealthy. It is nec¬ 
essary to make a close 
examination of indi¬ 
vidual stools to even 
begin to estimate the 
real damage. This is 
true especially of win¬ 
ter wheat, where many 
of the stems of the fall 
growth may be present 
only as dried and with¬ 
ered leaves. 
The injured culms 
are instantly recog¬ 
nized by the fact that, 
while the leaves, or at 
least part of them, are 
green and apparently 
healthy, the central 
stalk is dead and with¬ 
ered (fig. i). The in¬ 
jury done by C. femo - 
ralis appears identical 
with that of Meromyza americana until the leaves are examined. In 
each case the larva enters the leaf sheath by mining down from the point 
in the leaf where the egg was laid. If the injury is due to C. femoralis y 
the mine in the leaf is narrow, clean-cut, and almost straight; while if it 
is done by M. americana it is broad and irregular with indistinct edges. 
While M . americana enters the stem and eats out the central stalk, usually 
cutting it off above the first node, C. femoralis confines its attack to 
Fig. i.—Y oung wheat plant, showing (a) central stalk injured by the 
wheat-sheath miner, Cerodonta femoralis; ( 6 ) point where egg was 
laid; (c) mine in the leal made by larva on its way to the sheath; 
other leaves normal. 
