young leaves of cottonwood in the South, causing them to turn 
black, unfold improperly, and drop off frequently. Terminal 
growth is sometimes severely stunted. Mycodiplosis alternata Felt 
—produces clublike swellings on small twigs of dogwood. This 
sometimes kills several inches of the damaged twigs. 
Aphidoletes thompson Mohn, a European predator of the bal- 
sam woolly aphid, has been imported and is established in aphid- 
infested stands of Fraser fir in the Southern Appalachians. 
FAMILY XYLOPHAGIDAE 
ICHNEUMON FLIES 
These flies, as their common name suggests, often resemble 
members of the hymenopterous family, Ichneumonidae. The 
adults are usually observed feeding on sap, the nectar of flowers, 
or other liquid matter in forested or wooded areas. The larvae 
appear to be either predators or scavengers in rich soil, in decay- 
ing vegetable matter, under the bark of trees, or in decaying logs. 
Erinna lugen Loew larvae may occur in large numbers under the 
bark of elm in association with the elm borer. The larvae of 
E. abdominalis Loew feed on beetle larvae under the bark of pine. 
FAMILY STRATIOMYIDAE 
SOLDIER FLIES 
Soldier flies are brightly colored, moderately large, nearly bare, 
and thinly pilose. Many species are wasplike in appearance but 
the majority are broad and greatly flattened, and their wings lie 
parallel upon each other while at rest. These flies occur chiefly in 
wooded or forested areas or in meadows near water. Many are 
attracted to flowers. The larvae are usually terrestrial but some- 
times aquatic and act mostly as scavengers. Zabrachia polita Coq. 
has been reared from decaying pine logs and from beetle infested 
elm logs. 
FAMILY TABANIDAE 
HORSE F'LIES AND DEER FLIES 
Many members of this family are important blood-sucking 
pests of livestock and wild animals. Some species also attack man 
and can be extremely annoying. Their bites are sharp and painful, 
and many are capable of removing considerable quantities of 
blood from their hosts, especially when they attack in force. They 
may also transmit such animal diseases as anthrax, anaplasmosis, 
surra, swamp fever, and tularemia. 
Most of the large horse flies usually seen belong to the genus 
Tabanus. These flies breed mostly in marshes, swamps, bogs, and 
ponds. The largest and best known species is the black horse fly, 
T. atratus Fab. The adult is up to 25 mm. long and its bite can 
result in the loss of a considerable quantity of blood. In addition 
421 
