35 
and are only chance migrants to wheat from various wild grasses on 
which they normally feed. When seen, however, by the farmer they 
often arouse fears and are charged with damage with which, very 
likely, they have nothing to do. 
The adult insects are four-winged flies, belonging to the order 
Hymenoptera, which includes the bees and wasps. They are termed 
sawflies in description of the sawlike ovipositor of the female insect 
with which she makes incisions in the tissues of plants for the insertion 
of her eggs. The larvie of the species working on wheat either bore 
the stems or feed externally on the leaves. The stem-borers are the 
more distinctively wheat pests and are capable of doing much more 
damage. 
STEM-BORING SAWFLIES. 
Two species may be especially noted as being of possible importance 
in this country: First, the so-called European corn fly ( Cephus pygmeus) 
(fig. 22) and a native species ( Cephus occi- 
dentalis) which occurs in California and 
works in a similar manner in the stem 
of a hollow grass, probably a species of 
Elymus. 
The imported species, which is here 
better known as the European wheat 
sawfly, was first identified as occurring 
in this country about 1887 in New York? 
and shortly afterwards in Canada, and 
was carefully studied by Professor Com- 
stock at Cornell University. Up to the 
present time in this country it has never 
occasioned much loss. In Europe it is 
a well-known pest and, especially in 
France, is much feared. 
How they pass the winter—The adult f¥.% zuvmnn wists oa 
flies appear in April and deposit eggs in — ¢,same in wheat stalk; d, frass; ¢, adult 
the stems of the young wheat. The lar- Pte ie satiate ae ae 
ve bore through the joints and work up cated by hair lines (reengraved from 
and down the full length of the stem.  ‘°tl#! 
When full grown they attain a length of half an inch and are milky 
white in color. With approaching harvest they pass down to the bot- 
tom of the stem and cut the straw circularly on the inside, nearly sey- 
ering it. Beneath this cut they form a little cocoon at the base of 
the stem, within which they pass the winter in the larval stage, trans- 
forming to pup and emerging as adult insects in the following sum- 
mer, The object of the cut made just above their cocoon is to cause 

« The species was first collected in this country by Mr. F. H. Chittenden, at Ithaca, 
N. Y., about 1881 or 1882. (Ins. Life, Vol. IV, p. 344.) 
182 
