August, ’24] 
BLACKMAN: HICKORY BARK BEETLE 
461 
a tentative hypothesis supported if at all by only general observations. 
One attempt to correlate such an insect epidemic with a deficiency in 
rainfall was made by Felt (1914). 1 He shows that an outbreak of the 
hickory bark-beetle began in the vicinity of New York City in 1908 
and continued during the following four years. By a study of the 
Weather Bureau records for that locality he shows that: “From 1906 
to 1912 inclusive, there has been a deficient rainfall, except for 1907 at 
which time there was an excess of only half an inch. The total deficiency 
during this period amounted to 28.56 inches.” More significant still 
Felt shows that the deficiency in rainfall occurred mostly from June 
to September “During the growing months and at times most likely to 
affect vegetation adversely.” In conclusion he states: “With the 
above facts in mind it seems reasonable to believe that these unfavorable 
climatic conditions may have reacted upon the trees, reducing their 
normal resistance considerably and resulting in conditions which were 
extremely favorable to the multiplication of bark borers.” 
The observations and deductions of Dr. Felt were very interesting to 
the writer for at the time they appeared he had under observation at 
Syracuse a similar epidemic infestation of the same bark-beetle. These 
observations have been continued during the last eleven years, 1913— 
1923, and the data collected furnishes the basis for seme rather interest¬ 
ing hypothetical deductions. These deductions are based not only on a 
general study of the development and history of the infestation and a 
correlation of this history with meteorological data, but also takes into 
consideration the habits of the beetles during their larval and adult life, 
correlating this with weather conditions. The present writer also 
attempts to consider the physiological condition of the tree under 
different degrees of rainfall and the effect of these different conditions 
upon the attack of bark-borers. The deductions drawn are not pre¬ 
sented as proven facts, but are offered as a working hypothesis which 
may serve to stimulate future intensive investigations upon the inter¬ 
relations between climatic conditions and the development and control 
of bark-beetle infestations. 
The infestation of the hickory bark-beetle at Syracuse was first 
observed by the writer in September 1913. It occurred in a pasture 
woodlot of nearly four acres. The sparse stand, clay soil, steep slope, 
close pasturing and absence of underbrush made the conditions of 
growth quite unfavorable for hickory. In all there were about 165 
] Felt, E. P., 1914. Notes on Forest Insects. Journ. Econ. Ent. Vol. 7, pp. 
373-375. 
