THE COTTONWOOD BORER. 7 
the lower edge sunk into the ground about an inch. The top 
parts of the screen should be pinned to one another with small 
brads so as to fit closely about the tree; or they may be held in 
place by a piece of binding twine wrapped around them. The same 
screen cone will protect a tree for several years if made large 
at first; but the screens should be examined during June of each 
year, being loosened where too tight and repaired where torn. 
REMEDIES. 
When the 10 trees were examined in September, 1914, all eggs 
and young larvae were removed. (Table I.) Where possible the 
large larvae were also removed, and the number of eggs and larvae 
secured from each tree is noted in the table. The tunnels from which, 
owing to their depth, the larvae could not be removed were treated 
with a small quantity of carbon bisulphid injected from an oil can. 
From the 10 trees treated in this manner only five adults emerged 
during 1914, whereas from two untreated trees that were screened 
eight adults, or an average of four beetles to a tree, emerged. How- 
ever, the treatment with carbon bisulphid is of little benefit, as the 
larger larvae in tunnels from which they can not be removed have 
done, at this stage, nearly all the injury of which they are capable. 
The greatest benefit arising from the careful examination of the tree 
trunks lies in the removal of the immature borers that are working 
in the bark. This work is inexpensive and is entirely practicable 
for shade trees. 
SUMMARY. 
The injury by the cottonwood borer results from the adults ovi- 
positing in cuttings and very young trees, the young larvae cutting 
the bark and preventing the sap flow, and the larger larvae tunneling 
the wood, thus weakening the trees against wind. 
The eggs .are deposited in the younger trees principally during 
July and August. The larvae work in the trees until the second 
summer after the eggs hatch, when the adults emerge from about 
the middle of June until the 1st of August. 
Oviposition in shade trees may be prevented by screening the bases 
of the trees. The young larvae can be removed before they injure 
the trees severely if the -remedial work is done during the first two 
weeks of September, but removal of the large larvae from deep tun- 
nels often injures the trees more than would the larvae if allowed to 
remain and complete their development. 
WASHINGTON : GOVERNMENT PRINTING OFFICE : 1916 
