2 BULLETIN 1142, U. S. DEPARTMENT OF AGRICULTURE. 
phere, as in a room, the odor is quite pungent, irritating the mucous 
membrane to a considerable degree. 7 
REASONS FOR INVESTIGATION. 
In the course of the preparation and use of the tree-banding ma- 
terial, as well as of the last of the raupenleim, by members of the 
gipsy moth force, the question as to what constitutes the barrier factor 
in the band arose ; that is to say : What element or elements in the band 
halted the caterpillars in their attempted ascent to the foliage ? Was 
it the exhalation, or odor (chemical property) of the material; or 
was it its softness, or viscidity (physical property) ? Since the bands 
did not function as well in cooler weather or as they aged, was their 
decline in power or efficiency at such times due to their decreased vis- 
cosity, or firmer consistency; or was it due to the lessened odor? 
These questions had a practical bearing on the development of an 
efficient barrier, and attempts were made to obtain the desired in- 
formation by means of field observations. These, however, were not 
successful; indeed, they served only to develop decided differences 
of opinion. Nor was there any help to be had from European 
sources. Mr. L. H. Worthley, for instance, who spent the summer of 
1912 in Europe investigating gipsy moth conditions for the Bureau 
of Entomology, reported, on his return, that the forest authorities of 
Saxony and Bavaria regarded the odor as the effective element, or 
factor, in the band. But this information lacked applicability ; for, 
aside from the fact that these foresters dealt exclusively with raupen- 
leim, a material possessing a somewhat stronger or more pungent 
odor than the gipsy moth tree-banding material, their views were 
based largely, if not entirely, on the behavior of another species of 
insect, namely, the nun moth. It was possible, certainly conceivable, 
that the two species might differ in their reaction ; and an investiga- 
tion of the literature on the subject disclosed the propriety of the 
assumption, for, according to Judeich and Nitsche (4, P- S'45 1 888), 
such a difference of behavior exists, at least in the case of the nun 
and pine 8 moths, the caterpillars of the former, according to these 
authors, avoiding or shunning the raupenleim to a far higher degree 
than those of the latter. The uncertainty, it might be added, was 
somewhat further increased, in view of the further statement of 
Judeich and Nitsche (ibid.) that "Die Nonnenraupen vermeiden jede 
Beriihrung des Leimes * * *," by the statement cf Eatzeburg 
(#, p. 52) to the effect that some of the caterpillars of the nun moth 
will brave the odor of tar. Because, therefore, of the lack of definite 
knowledge and the uncertainty and of the practical bearing that such 
knowledge had on the elaboration of an efficient barrier, it was 
deemed advisable to investigate the matter. ; 
THE PROBLEM. 
That the odor of the material exercises a restraining influence 
could not be doubted. Neither, on the other hand, could one with a 
7 The term "odor" is used here in the common or ordinary (and older) sense, inclu- 
sive of the irritating quality of the material as perceived by the nasal mucous membrane. 
Properly speaking, of course, the latter property of materials is not generally olfactory 
(5, p. 165, 169). In this connection the writer wishes to thank Prof. G. H. Parker, pro- 
fessor of zoology, Harvard University, for the courtesy of allowing him to read portions 
of his forthcoming book dealing with the chemical sense in vertebrates and for other sug- 
gestions. 
8 Bomtyx pini L. (" der Kiefernspinner "). 
