INSECT ENEMIES OF EASTERN FORESTS 509 
Famity ITONIDIDAE 
The Gall Midges 
According to Felt (748, 150, 151, 153), whose extensive papers on 
American galls have furnished the data for this compilation, there are 
about 900 native species of Itonididae, 700 of them having been reared. 
The habits of the species vary greatly. Practically any part of the 
tree may be affected. There may bea gall, a pronounced swelling, or 
a mere shrivelling of the living tissue. Some species are found only 
in the seeds or cones, whereas others live in exposed positions on the 
leaves or in small pitch patches that exude from injured limbs. A 
few species live in dead wood. 
The adults of this family are small, slender flies, resembling mos- 
quitoes in many respects. They usally have long antennae and broad 
wings, the latter usually with few longitudinal veins and with or with- 
out across vein. T he tibiae are without terminal spurs. 
The larvae range in color from white to orange. The body is 
slender and somewhat flattened, tapering at both ends. The mouth 
parts are vestigial or suctorial. The principal character of the mature 
larva is the presence of a chitinized structure on the ventral side of 
the anterior end, called the “breastbone.” This organ is believed to 
function as a boring tool, but it is also often used to lacerate or scrape 
plant tissue, thus causing a flow of sap on which the larva feeds. The 
larvae of some species are further characterized by their ability to 
spring into the air for a short distance. 
There have been many rearings of Itonididae from recently cut 
logs or from decayed wood of various kinds. The closely packed 
larvae of an undetermined species have been observed beneath elm 
bark in numerous old tunnels of Hylurgopinus rufipes. This species 
appears to be predaceous and is not to be confused with the paedo- 
genetic species of J/7astor, which lives in colonies beneath the bark of 
decadent trees or stumps and can be readily recognized by the general 
absence of a “breastbone,” which is present in a few individuals only. 
Relatively few of the gall midges are injurious. Control measures 
are seldom necessary, since the infestation usually disappears after 
a few years. However, when abundant, the galls may frequently mar 
the appearance of the tree and cause considerable apprehension. 
Individuals other than the specialist may best identify the species 
by means of the host plant and type of gall. This is a more or less 
reliable guide, since most species are restricted to a single host or its 
near relatives. A few species reported as injurious, and a few others 
mentioned because of their occasional abundance, are described here, 
and are grouped under the host plant instead of by genera, as is done 
in the remainder of this publication. 
ABIES (FIR) 
9 
The larva of J/tonida balsamicola (Lint.), the balsam gall midge 
is inactive and produces subglobular, basal swellings of about 3 mm. 
diameter at the bases of the leaves (fig. 129). The species is not 
believed to be particularly injurious, although it has been reported 
as abundant on balsam fir in the Adirondack Mountains in New York. 
