INSECT ENEMIES OF EASTERN FORESTS 139 
Famity ALEYRODIDAE 
THE WHITEFLIES 
These very small, four-winged insects, are almost entirely leaf 
feeders. As forest insect pests they are of little concern. Two species 
that might be mentioned are Alewrochiton forbesii (Ashm.), which 
feeds on maples, and 7etraleurodes mori (Quaint.), the mulberry 
whitefly, which sometimes infests maples, mountain-laurel, ash, mul- 
berry, and dogwood. 
SuperFAMILY COCCOIDEA 
Scale insects are among our most destructive agents of ornamental 
or shade trees, and at times may cause extensive damage to forest 
growth. Injury may be caused either by the mere withdrawal of 
plant juices from the host by large numbers of insects or by their 
production of galls while feeding. 
Male insects in this group are usually winged, but the females are 
entirely wingless. During metamorphosis many adult females lose 
their appendages; and, even when they do not, the appendages are 
atrophied. As a result, the females of many species never change 
position after once inserting their beaks or stylets into the host plant. 
The female body is scalelike, or gall-like, and is covered with wax, 
either in the form of powder, tufts, plates, or a thin layer covering 
the insect and beneath which it lives. Although the insect is not 
formless, it is often difficult to separate the body into head, thorax, 
and abdomen. In many species the mouth parts appear to emerge 
from about the center of the body. 
Some species in this group are highly specific in host selection; 
others are more generalized and feed on a wide variety of hosts. 
Through their habit of feeding on many different parts of plants, 
many species have become nearly world-wide in their distribution, 
having been transported with nursery stock or cuttings (McDaniel, 
285, Marlatt, 289; Morrison, 306; Sanders, 373; and Trimble 474). 
Famity MARGARODIDAE 
The individuals of some species in this family are quite large. The 
cottony-cushion scale (Zcerya purchasi Mask.), which sometimes in- 
fests shrubbery, measures from 4 to 8 mm. in length (fig. 30). 
Several species in the genus A/atsucoccus have received considerable 
attention in recent years as pests of forest trees. So far as known, 
members of the genus live only on species of pine. The pine twig 
gall scale (Matswcoccus gallicola Morrison), is one of the more 
important species in this group. It attacks pitch, shortleaf, table- 
mountain, Virginia, ponderosa, loblolly, and spruce pines, and is dis- 
tributed from New England west to Ohio and Missouri and south 
to Florida and Georgia. 
Mature females of the pine twig gall scale are generally much 
flattened and are from 2 to 5 mm. long. They deposit their eggs 
under bark scales on the larger branches and trunks of infested trees, 
and these hatch early in the spring, about the time the host tree begins 
to grow. 
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