INSECTS AFFECTING OAK-ROOTS. 49 
records for Germany. It is not improbable that ultimately the number 
of species for the United States will be between 600 and 800 or even 
1,000. 
We will now briefly indicate those species of insects which are habit- 
ually more or less destructive to the oak. 
The roots of the live and probably the water oak are infested by the 
great longicorn borer, Mallodon melanopus, the trees being permanently 
dwarfed and their growth arrested. 
Of the borers in the trunk, the caterpillar of the Carpenter moth 
(Prionoxystus robinice) probably does more damage than all other borers 
combined. Next to this borer, come the flat- head borers, and. the bark- 
borers, with the oak-pruner (Elaphidion villosum), while the seventeen- 
year Cicada periodically prunes or destroys many of the twigs. 
The leaves suffer most from the attacks of the forest tent-caterpillar 
{Clisiocampa disstria) aud the large black- and-red-striped spiny cater- 
pillar of the senatorial moth (Anisota senator ia). These two caterpillars 
in the Atlantic aud Central States as a rule do more harm to oak for- 
ests than perhaps all the other species combined. 
Finally, many acorns are worm-eaten, the intruder being the grub of 
the long-snouted weevil (Balaninus). We have, so far as practicable, 
described the habits and appearance of the most destructive species 
first. 
AFFECTING THE ROOTS. 
The roots of various species of oak are, without much doubt, more 
or less injured by the attacks of the seventeen-year Cicada while in its 
preparatory state, as it is known that this insect, so abundant in the 
central and southern States of the Union, remains for over sixteen 
years attached by its beak to the rootlets of the oak and probably other 
forest trees, where it sucks the sap, thus in a greater or less degree in- 
juring the health of the tree. Observations as to the subterranean 
life of the seventeen-year locust are few aud obscure, and it is quite 
uncertain how much injury is really done to trees by this habit. They 
have sometimes been found sucking the sap of forest trees, notably the 
oak, and also of fruit trees, such as the pear and apple. According to 
Riley (First Keport, p. 24), the larvae are frequently found at great depth, 
sometimes as much as 10 feet below the surface. It has been claimed 
by Miss Margaret! a H. Morris, in an account published in 1846, that 
pear trees have been killed by the larvae sucking the roots. This has 
been denied by the late Dr. Smith, of Baltimore, who says : 
The larva obtains its food from the small vegetable radicels that everywhere per- 
vade the fertile earth. It takes its food from the surface of these roots, consisting of 
the moist exudatiou (like animal perspiration), for which purpose its rostrum or snout 
is provided with three exceedingly delicate capillaries or hairs, which project from 
,the tube of the snout and sweep over the surface, gathering up the minute drops of - 
moisture. This is its only food. The mode of taking it can be seen by a good glass. — 
Prairie Farmer, December, 1851. 
5 ENT 4 
