EXPERIMENTS WITH SPRAY SOLUTIONS FOR GREEN LOGS. 5) 
problem and the preliminary experiments conducted during the 
years 1916 to 1919 are here presented. 
REQUISITES OF A PRACTICAL SPRAY. 
It may be impossible to find a single spray solution that can be 
used with success under all conditions, but it may be possible to 
obtain good results by using several solutions, each of which is effec- 
tive under certain conditions. Any spray to fulfill all the requisites 
necessary for practical effectiveness must possess the following qual- 
ities: 
IT MUST BE EFFECTIVE AGAINST SEVERAL TYPES OF INSECTS. 
Many species of insects attack green timber. Some attack only 
certain kinds of wood while others show httle discrimination. In 
some cases the injury is caused by the grubs or larve feeding be- 
neath the bark or in the wood, or by an adult which bores through 
the bark and produces larve that feed under the bark. According 
to their method of attacking the wood, boring insects may be divided 
into the following four groups: 
Type 1. Those that lay eggs in crevices of the bark. The larve 
hatching from these eggs then bore through the bark and later into 
the wood. 
Type 2. Those that gnaw a hole through the bark and insert the 
egg beneath. The larve start feeding directly beneath the bark and 
later bore into the wood. 
Type 3. Those that bore through the bark and wood as beetles, 
to make a suitable place for developing a new brood. The grubs in 
this case never cause injury. 
Type 4. Those that bore through the bark as beetles and lay the 
eggs beneath the bark. The resulting larve feed beneath the bark 
and loosen it. 
The only spray that could possibly be effective against all these 
types would be one of a disagreeable odor acting as a repellent, thus 
driving away the adult beetles and preventing oviposition. Poison 
sprays that will penetrate the outer layers of bark will kill the young 
larvee of type 1, but experiments have demonstrated that such mate- 
rials are not effective against types 2, 3, and 4. In these types most 
of the beetles do not eat any of the bark or wood as they chew 
through it and consequently are not poisoned. Possibly a poison 
combined with a sticky substance that would form a film over the 
bark and adhere to the mouth parts of the insects might kill them. 
Insects of type 4 are not very injurious to saw logs, as they only 
work beneath the bark and do not enter the wood, but they are 
important in loosening the bark from rustic work. The odaets are 
all injurious to both classes of timber. 
