BARRIER FACTORS IN GIPSY MOTH TREE-BANDING MATERIAL. 6 
knowledge of the habits and behavior of insects and the action of 
banding materials in general doubt that the soft and semiviscid con- 
dition of the material acts as a bar. As it presented itself to the 
writer, therefore, the problem seemed to be really a matter of deter- 
mining the relative values of the two factors; that is, which of the 
two is primary and will by itself constitute the effective, or the more 
effective, barrier against the gipsy moth caterpillars. As to pro- 
cedure, the problem appeared to be a matter of devising a material 
with an odor like or very similar, and similar in degree of pungency, 
to the gipsy moth tree-banding material which would readily solidify 
or stiffen without material^ losing in the process its odor- emitting 
quality, and this was to be used against the caterpillars in the form 
of firm or more or less solid, odorous bands, in connection with 
odorless check bands, both viscous and solid. 
EXPERIMENTAL WORK. 
The basal solid ingredient which suggested itself as possibly best 
meeting the requirements for such a material was ordinary white 
wheat flour. Flour is itself odorless, possesses the property of 
readily becoming firm, or of solidifying after being mixed with 
ordinary liquids, and is very easily obtained. Furthermore, it can 
very easily, by merely mixing with water, be made into a soft and 
somewhat pasty odorless material which can be utilized for check 
bands. 
Accordingly, such flour 9 was mixed with coal-tar neutral oil or 
with a mixture of coal-tar pitch and coal-tar neutral oil, and placed 
in the form of bands on sheets of white paper laid on a horizontal 
surface and also around peeled upright wooden stakes. White 
paper and peeled stakes were used merely to facilitate observation. 
The caterpillars tested included all stages, beginning with the sec- 
ond. Soft and semiviscid odorless bands, made of flour and water, 
of flour and molasses, and of molasses alone, were used as checks. 
In summarizing the results of these tests, it may oe said that the 
stiff or solid odorous bands, while exercising a repellent and restrain- 
ing influence to a considerable degree, proved no absolute bar to the 
caterpillars. The soft and semiviscid odorless bands, on the other 
hand, were never crossed, although they were approached with far 
less hesitation and were, on the whole, touched more often and were 
even eaten. The bands on the horizontal surface were crossed more 
readily than those placed in the form of rings on the upright stakes, 
and, in general, the bands were less effective against the larger or 
more advanced stages of the caterpillars. The letter statement ap- 
plies more particularly to the horizontal bands. The caterpillars — 
the larger ones in particular — seemed to have some difficulty in main- 
taining a " foothold " on the bands on the stakes, but this seems to 
have been due, in part at least, to the yielding and somewhat friable 
nature of the bands. 
SERIES I. 
The following illustrations, taken from numerous experiments or 
tests, will show in a detailed way the behavior of the caterpillars 
with reference to the stiff or solid odorous band series. 
9 Putty, as a substitute for flour, was later also used but proved less satisfactory. 
