Grass Stem Flies

(Family Oscinidae.)
These are little flies, either dark and shining or yellowish in color, and are more or less stout-bodied. The larvae breed in the stems of grasses or are found in decaying vegetable material; some live in the burrows or cavities in plants made by other insects while a few feed on the egg shells and cast skins of insects. Meromyza americana feeds in the stems of wheat and rye, and sometimes does considerable damage; the larva of Chlorops graminea lives in a gall-like swelling on grass stems, and the larva of Chlorops assimilis mines the leaves of sugar beet. One of the commonest of these flies in this country is a little scavenger known as Gaurax anchora, which feeds upon all sorts of dead animal matter, such as the empty egg shells of other insects, the cast-off skins of caterpillars and chrysalids, and spiders' eggs.

The little flies of the genus Hippelates are especially noticeable in the summer time, particularly in the Southern States. They are the most minute of flies, and swarm about the eyes of dogs and domestic animals, and in some places are annoying by getting into the eyes of human beings.

The species of the true genus Oscinis almost invariably in their larval stage bore into the stems of living plants, especially grasses, but one species lives in the seed pods of the so-called Indian bean tree (Catalpa speciosa). A member of this family is the famous "frit fly" of Europe, and causes great damage to grain crops, especially in North Europe.