378 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
environment is well illustrated by the insect life in logs, particularly by 
those insects that live just beneath the bark. The presenc paper is 
based upon a series of experiments carried on in Itasca Park, Minne¬ 
sota, at the University of Minnesota Forestry School and Experiment 
Station. These experiments have extended over a period of four years, 
during which time considerable data concerning the effect of physical 
factors of the environment upon insects attacking logs have been ac¬ 
cumulated. 
For the purpose of this article it seems desirable, for the sake of 
simplicity, to select for discussion only a few insects, representing several 
ecological groups. The insects included in the experiments just men¬ 
tioned that seem to best satisfy our requirements are as follows: 
1. Ips pini Say 
2. Monochamus scutellatus Say 
3. Chrysobothris dentipes Germar 
These species are very abundant and reacted very definitely to 
temperature conditions. 
The Effect of High Temperatures 
Before we can interpret field observations correctly we must usually 
have as a basis laboratory experiments. This study of temperature 
effects is no exception, and a knowledge of temperatures fatal to those 
insects that we are considering is essential. As all of the observations 
upon which this paper is based were made during the summer season, 
the effect of extremely low temperatures is not considered. 
Table I illustrates the effect of high temperatures upon the adults 
and larvae of these three species. 
Table 1. Fatal High Temperatures in °C 
Species 
Stage 
Minimum death 
Average death 
Maximum death 
temperature 
temperature 
temperature 
(Adult 
43 
47 
50 
Monochamus scutellatus■ 
\ Larvae 
45 
48 
50 
Ips pint . 
jAdult 
44 
48 
50 
I 
l Larvae 
44 
.46 
49 
Chrysobothris dentipes.. 
j Adult 
«Larvae 
45 
50 
52 
These figures show a considerable individual variation in death 
temperature in both the adult and larval stages. Cases must fre¬ 
quently occur in nature where an entire brood would be destroyed if it 
were not for some of those exceptional individuals that fall without the 
