208 
TREES AS GOOD CITIZENS 
lemon-yellow. They settle on leaves and 
twigs, feeding there until late summer, 
when they return to the trunk or larger 
limbs. 
GALL INSECTS 
Gall Aphids 
Habits These sap-sucking insects 
and disfigure a tree by causing the 
Damage, growth of swellings known as 
galls. These galls sometimes 
become so numerous as to create alarm, 
but the damage is more to appearance 
than to growth or vitality. A tree is sel¬ 
dom harmed in health by them. 
Remedies. Spraying is seldom neces¬ 
sary but if desired a tree may 
be sprayed with kerosene emulsion or mis¬ 
cible oil solution. If the galls appear on 
more than one tree in a neighborhood all 
of those infested should be treated. 
GUM (SWEET) 
LEAF-CHEWING INSECTS 
Forest Tent Caterpillar 
(See description and remedies under Elm) 
HACKBERRY 
LEAF-CHEWING INSECTS 
Spiny Elm Caterpillar 
(See description and remedies under Elm) 
Hackberry Butterfly Caterpillar 
Habits This leaf-chewer causes ser- 
and ious damage to the foliage of 
Damage, the Hackberry. Two genera¬ 
tions develop yearly, from 
eggs deposited on the leaves. The cater¬ 
pillar is green in color, with pale spots and 
lines along the back and projections at 
each end. It is found on the under side 
of the leaf. At maturity the caterpillar 
develops into a russet gray butterfly, 
spotted with brown. The presence of the 
caterpillar is indicated by the damage 
resulting from its leaf-eating habits. 
Remedies. These caterpillars fall to 
the ground with the dropping 
leaves in the autumn and it then becomes 
a simple matter to destroy them by raking 
and burning the leaves. Spraying the 
tree with lead arsenate while the cater¬ 
pillars are feeding is also a means of 
control. 
GALL INSECTS 
Hackberry Gall Insects 
Habits The galls produced by this 
and insect mar the appearance of a 
Damage, tree by disfiguring the foliage, 
but otherwise they do no par¬ 
ticular harm. In the spring, when the 
buds begin to swell and open, the insect 
Remedies. It is not often necessary to 
apply treatment against this 
insect, as the damage is usually slight. 
When treatment is needed the tree should 
be sprayed with kerosene emulsion or 
water-soluble oil. The spray should be 
