Pachypsylla venusta (O.8.), the petiolegall psyllid, is the largest 
of the hackberry psyllids, and it forms the largest galls. The galls 
are polythalamous and usually contain six cells. Sometimes there 
are as many as 30. These galls may persist on the trees for several 
years and seriously damage the appearance of shade trees. Dis- 
tribution of the species is mostly limited to below the 40th parallel. 
Pachypsylla celtidisinteneris Mally forms small, inconspicuous, 
monothalamous galls under the bark of twigs. 
Several species in the genus Psylla also feed on various trees, 
shrubs, and ornamentals. Large quantities of honeydew are pro- 
duced which drip down and cover their hosts. A black mold grow- 
ing in this material often makes infested plants look unhealthier 
than they are. 
The boxwoed psyllid, Psylla buat (L.), attacks American and 
English varieties of boxwood, and probably occurs wherever they 
grow. The adult is greenish and has transparent wings; nymphs 
are gray-green and covered with a white cottony or waxy ma- 
terial. The first winter is spent in the nymphal stage. Feeding is 
resumed in the spring and adults begin to emerge in early May. 
Infested leaves curl and form cups in which nymphs are concealed. 
Feeding also results in reduced growth of young twigs. Eggs are 
laid under bud scales during July and August. Weiss and St. 
George (752) discuss methods of control. Other species of Psylla 
and their hosts include: P. annulata Fitch, paper birch and maple; 
P. carpinicola Crawf., birch; P. floccosa Patch and P. galeaformis 
Patch, alder; and P. trvimaculata Crawf., wild cherry. 
Trioza tripunctata Fitch has been observed feeding on the 
needles of pines in ornamental plantings in Connecticut. Damage 
consists of yellowish or reddish spots which frequently coalesce, 
causing the needles to die and drop prematurely. The persimmon 
psylla, T. diospyrt (Ashm.), and T. magnoliae (Ashm.) feed on 
persimmon and magnolia, respectively, in Florida. 
Psyllids are attacked by a large number of hymenopterous and 
dipterous parasites. Jensen (402) listed more than 150 species 
from the United States alone. 
FAMILY APHIDIDAE 
APHIDS, PLANT LICE 
The aphids or plant lice constitute a very large group of small, 
soft-bodied insects that feed by sucking the sap from the leaves, 
stems, and roots of plants and trees. They are pear-shaped, have 
fairly long antennae, and a pair of tubelike cornicles rise from 
the top of the fifth or sixth abdominal segment. Winged males are 
common. The wings are very delicate and membranous, with only 
a few simple veins, and they are usually held vertically above the 
body while at rest. Egg-laying females of many species are also 
winged. 
Ordinarily, most of the aphids feed exposed on their hosts. 
Others feed in sheltered locations such as inside leaves, which 
they cause to curl or to become distorted, or inside galls. Trees of 
all kinds, sizes, and ages are attacked, but they normally are not 
seriously injured. Serious damage sometimes results, however, 
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