INSECT ENEMIES OF EASTERN FORESTS 535 
FamMity EMPIDIDAE 
Dance Flies 
The family Empididae is a large family, most of the species of which 
have spherical heads, large eyes, piercing mouth parts, and the mystax 
weak or absent. The abdomen and legs are slender, and the cubital cell 
is short. The larvae of the empids are cylindrical; they taper an- 
teriorly and have small, retractile heads. 
Very little is known regarding the early stages, but a good many of 
them are believed to be predatory. A few species are aquatic. 
Tachydromia sp. has been bred from weeviled white pine leaders, 
Rhamphomyia dimidiata Loew and Drapetis nigra Meig. from rotten 
tree stumps, and Platypalpus aequalis (Loew) from decayed hickory. 
As in the chironomids (p. 540) the species of several genera are fre- 
quently observed in swarms, dancing up and down under the trees and 
shrubs near brooks or standing water. 
Famity DOLICHOPODIDAE 
The Long-Legged Flies 
The dolichopods are small, bristly flies, usually of a metallic greenish 
color. The absence of a cross vein between the discal and second basal 
cells of the wing serves to distinguish the members of this family from 
their nearest allies. The larvae are cylindrical and resemble the 
empids, from which they are difficult to separate. They are terrestrial 
or aquatic and not much is known about any of the immature stages. 
Species of the genus 7hrypticus are found in the stems of plants, and 
Medetera sp. was reported by Blackman and Stage (45) as bred from 
larch wood infested with Polygraphus rufipennis Kby. and Eccopto- 
gaster piceae Swain. It is believed that M/. nigripes Loew is a primary 
parasite of P. rufipennis. Dolichopus vittatus Loew and several un- 
determined species were reported (Blackman and Stage, 46) as bred 
from dead, beetle-infested hickory. 
Faminry THEREVIDAE 
Stiletto Flies 
The Therevidae, or stiletto flies, resemble the asilids, being dif- 
ferentiated by their plane or convex front, nonprotuberant eyes, and 
usually fleshy labellae. The posterior branch of the third vein ends 
beyond the tip of the wing. 
The larvae (fig. 128, A’) are long and slender, tapering at both ends, 
and move about in a snakelike manner, not drawing their bodies to- 
gether as do most Diptera. Late-instar larvae have been found in the 
soil, in decaying wood, and in various other environments. On one 
occasion seven therevid larvae were collected beneath the bark of a 
practically dead elm. In the West several species have been reported 
as predaceous on elaterid larvae. 
Famity OMPHRALIDAE (SCENOPINIDAE) 
Window Flies 
The Omphralidae, or window flies, are small to moderate-sized 
bare flies, usually blackish in color, with the antennae destitute of 
