The apple maggot, Rhagoletis pomonella (Walsh), an important pest of apple, 
also breeds in the fruit of hawthorn, common chokecherry, plum, and dogwood. 
The adult is dark colored and a little smaller than the house fly. Each wing is 
crossed by four dark bars that merge together. Three or four white bands run across 
the dorsum of the abdomen. The cherry fruit fly, R. cingulata (Loew), breeds in 
the fruit of cherry. Adults are black except for yellow margins on the thorax, two 
white crossbands on the abdomen, and a dark band on each wing. They are smaller 
than house flies. The black cherry fruit fly, R. fausta (Osten Sacken), breeds in 
cherry throughout the same area as does the cherry fruit fly. Adults resemble those 
of the cherry fruit fly except for the abdomen, which is entirely black. The walnut 
husk fly, R. completa Cresson, breeds in the husks of black walnut in the Central 
States. Feeding by the larvae produces a slimy condition that causes the husks to 
turn black, stick to and stain the shell. Nuts with damaged shells cannot be sold 
even though the contents are sound. The wings of the adult are transparent with 
dark crossbars. Toxotrypana curvicauda Gerstaker breeds in papaya in Florida and 
Texas. 
Family Chamaemyiidae 
Aphid Flies 
The larvae of a number of species in several genera of these small, yrayish flies 
are predators of aphids, scale insects, and mealybugs. One species, Leucopis 
obscura Haliday, a native of Europe, was introduced into Canada against the 
balsam woolly adelgid in the early thirties. It quickly became established and, 
following additional colonizations, spread over most of the infested areas in eastern 
Canada and into northern New England. Since 1954, colonies have been released in 
adelgid-infested stands in Vermont, New Hampshire, New York, North Carolina, 
and the Pacific Northwest. It is usually found on heavily infested trees only, where 
it feeds mostly on adults that have laid many eggs. 
Cremifania nigrocellulata Czerny, another European species, also imported into 
eastern Canada and the Pacific Northwest against the balsam woolly adelgid, is now 
established. A fairly large number have developed on stem-infested trees, but their 
spread has been very slow. 
Family Lonchaeidae 
Lonchaeids 
Adults of this family are shiny black and about 5 to 6 mm long. The larvae are 
very small and are covered by minute spines. These flies act mostly as scavengers 
or as predators on other insects. Lonchaea polita Say has been reared from bark- 
beetle infested wood. L. corticis Taylor has been recorded as an important parasite 
of the white pine weevil (762). 
Family Drosophilidae 
Vinegar Flies 
These are the flies that are so often seen around spoiled fruit, slime fluxes, and 
fungi. Usually yellowish except for black markings on the abdomen, adults seldom 
exceed 5 mm in length. Few if any species are of importance as enemies of forest, 
shade, or ornamental trees. There is a possibility, however, that certain species are 
involved in the transmission of the oak wilt fungus, Ceratocystis fagacearum 
(Bretz) Hunt (507). Members of the genus Drosophila are very important in the 
field of genetics research. 
Family Chloropidae 
Chloropid Flies 
These flies are small to very small with numerous clothing hairs and some 
bristles. Some species are brightly colored with yellow and black. The larvae of 
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