a 
Insects of Shade Trees and Their Control. 91 
general distribution entail heavy infestation at some place in the 
country each season, with consequent frequent inquiry as to the 
cause and remedy, so that consideration of them here is made 
necessary, if for no other reason, to allay the prevailing fear of the 
consequence of their attack. The similarity of effect and economic 
relation invite joint consideration of all hickory gall insects. 
Seasonal history and habits. 
Phylloxeridae.—F rom early June of one year to early April of the 
next, or about 10 months of the year, is passed by these insects in the 
egg stage located in cracks and crevices, old galls, etc., on the hickory 
tree, particularly on the upper part of it. Coincident with the burst- 
ing of the buds in the spring these eggs begin to hatch, and the larve 
ultimately become the so-called stem mothers. These stem mothers 
settle on the young twigs, leaf stems, midribs, or forming nuts and 
each of them starts the formation of a gall with an inner cavity. In 
about 20 days from the time the gall is started the stem mothers de- 
posit large numbers of eggs from which, in about 20 days, a genera- 
tiori of winged, migrating females develops. By this time the gall 
begins to open, thus allowing the insects to escape and fly. These 
migrants in turn lay eggs on the trees, and in about 10 days the young 
develop into wingless males and females and the mature females lay 
fertile eggs, which remain on the tree until the following spring, when 
the complicated life cycle is repeated. Most of the known species of 
this group infest hickory trees. 
Itonididae.—Very little is known about the habits of the hickory 
gall midges except that, where an egg is laid and a larva hatches 
from it and develops, the plant tissue produces abnormal growth 
resulting in a larger or smaller gall, constant in shape and in other 
respects for each given species. 
Artificial control—Under wild or forest conditions artificial con- 
trol is entirely impracticable and unnecessary, but in the case of 
valued shade or nut-producing trees that are regularly infested by 
the galls, it may be desirable to spray the trees with kerosene emul- 
sion (p. 12-13) at the time the buds are opening in the spring, which 
should kill the stem-mothers or young maggots, as the case may be, 
and thus prevent the development of the galls. 
HACKBERRY GALL-INSECTS.” 
How injurious—The galls made by this group of insects occur 
only on hackberry trees. In general outer appearance these galls do 
not differ from the almost equally numerous fly galls that occur on 
these trees, nor are they more injurious. They occur on the leaves, 
leaf stems, and twigs and, when very numerous, disfigure the appear- 
ance of the foliage, but that is about all the harm they do. 
© Pachypsylla spp. 
