livestock and people included. During intervals between outbreaks, the species is 
hard to find. In the Southern States, the related species, S$. houghi Aldrich, 
parasitizes the forest tent caterpillar and elm spanworm. 
Family Tachinidae 
Tachina Flies 
The family Tachinidae contains many of the most important species of insect 
parasites. All species appear to be internal parasites of many kinds of insects, 
especially Lepidoptera, but also various species of Coleoptera, Hemiptera, Orthop- 
tera, and Hymenoptera (/049). 
Tachinid flies look very much like house flies but many differ in having an 
entirely bare arista; however, the arista on some species may be pubescent or as 
plumose as that of house flies. The maggots are clothed with minute spinules, and 
the posterior spiracles are flush with or raised from the adjacent area. 
The majority of species are oviparous, but a few give birth to living young. Eggs 
are deposited on the skin of the host, on leaves or other parts of plants on which 
their hosts feed, or on the soil. Living young are deposited on or under the skin of 
the hast. on leaves and other parts of plants frequented by their hosts, or on the 
ground. The number of generations per year varies from | to 10, depending on 
species and climate. 
A large number of native species and a few introduced species parasitize various 
native and introduced species of eastern forest insects. More than 125 species have 
been recorded attacking lepidopterous larvae in this country (/062, 1063). A few of 
the more important introduced species are discussed here. 
Compsilura concinnata (Meigen) (fig. 217) was imported against the gypsy and 
browntail moths early in this century. It is now widely distributed throughout most 
of the Northeast and in southeastern Canada where it attacks at least 200 species of 
Lepidoptera. Parasitization of the gypsy moth averages from 10 to 50 percent in 
F-519564 
Figure 217.—Adult and puparium of Compsilura 
concinnata, a parasite of the gypsy moth and other 
defoliators. 
452 
