"4 Farmers’ Bulletin 1169. 
sisting attack. The attack can not be successful, therefore, unless 
the vitality of the tree is low at the time of attack or unless the beetles 
are sufficiently numerous to overwhelm a healthy tree. An abundance 
of sickly, dying, or felled hickory trees in the near vicinity provides 
favorable conditions for the production of an excess of beetles. 
Control.—The evident means of checking the ravages of this pest 
is to keep the beetles down below a number sufficient to attack vig- 
orous trees successfully. This can be accomplished (1) by putting 
into practice the very important principle of forestry of prompt, 
systematic removal from the area and disposal of all hickory trees 
which show signs of decline, and (2) by cutting and utilizing, for 
firewood -or otherwise, the badly 
infested trees in the area. 
SAP-SUCKING INSECTS. 
GENERAL. 
The feeding of sap-sucking in- 
sects on deciduous shade trees is 
not manifested by visible holes in 
leaf or bark, but usually by dis- 
colored or wilting foliage and gen- 
erally by the sickly and often black, 
dirty appearance of the trees. As 
these insects do not feed on plant 
tissue but on plant sap, which they 
secure from the inner tissues by 
thrusting their beaks through the 
Fig. 58.—Sycamore lace-bug: Adult, outer layers, they can not be de- 
greatly enlarged. (Wade.) : ve ae ‘ 
stroyed by poisoning the foliage of 
the trees on which they live but must be hit directly by substances 
which kill on coming in contact with their bodies and which, there- 
fore, are known as contact insecticides. 
SYCAMORE LACE-BUG.“ 
How injurious.—By no means can the sycamore lace-bug be called 
a tree-killing insect, but great numbers of it not only discolor the 
foliage of the sycamore, its only host tree, but also cause premature 
falling of the leaves, thus rendering the tree unsightly and littering 
the ground beneath it. It may be found on sycamore, especially 
Platanus occidentalis, wherever it grows in the United States. 
How recognized—The sycamore leaves are off color in irregular 
spots or entirely and the underside is inhabited by colonies of queer, 
rather slow-moving bugs with prettily marked, lace-like horizontal 
wings (fig. 53), or their offspring with larger or smaller wing pads. 
46 Corythuca ciliata Say. 
