INFLUENCE |0F TEMPERATURE AND EVAPORATION 
UPON THE DEVELOPMENT OF APHIS POMI DEGEER 1 
By Frank H. Lathrop 2 
Associate Entomologist , Oregon Agricultural Experiment Station 
INTRODUCTION 
Entomologists attacking economic problems are ever impressed with 
the need of a more thorough knowledge of the influence of the environ¬ 
mental factors which control the activities of the insects under investi¬ 
gation. The interrelations between insects and their environment are 
highly complex, and attempts at their determination are fraught with 
many difficulties. That any effort in this direction is well worthy of the 
expense in time and energy there can be little doubt, for, while this is 
as yet a comparatively unexplored field, there are many instances of 
the application of a knowledge of environmental factors to the applied 
control of economic pests. Headlee 3 pointed out the possibilities of the 
reduction of certain stored grain pests by modifying the relative humidity 
of the air within the container. Lovett and Fulton, 4 in discussing the 
control of the codling moth in the Willamette Valley, state: 
Where the evening temperature during May at 8:oo p. m. is 6o° or above, the first 
generation codling moths may be expected to deposit eggs. Consequently when this 
temperature of 6o° at 8:oo p. m. is registered, it is the proper time to apply the 
‘‘thirty-day ” codling moth spray. 
A realization of the economic bearing of such information prompted 
the writer to make observations of certain climatic factors in connection 
with a study of the activities of several species of apple aphids, a group 
of insects which seem especially susceptible to climatic influence. A 
considerable amount of data on evaporation, temperature, and pre¬ 
cipitation has been collected which, aside from the bearing upon the 
present study, should be of considerable general interest to both plant 
and animal ecologists. 
In order to concentrate the study and to avoid scattering the data 
over too broad a field, observations in this connection were practically 
limited to a single species Aphis pomi DeGeer. 
An understanding of the fundamentals of the life history of the species 
is desirable in considering the data here presented. For this reason the 
seasonal cycle is briefly reviewed. 
1 Accepted for publication Jan. 16,1922. 
* The writer is indebted to Prof. A. L. Lovett for encouragement in the prosecution of this study, and 
to Mr. Richard Jones whose painstaking work as Technician in the Department of Entomology relieved 
the writer of much of the routine work of this study. 
* Headlee, Thomas J. some pacts relative to the influence of atmospheric humidity on insect 
metabolism. In Jour. Econ. Ent., v. 10, no. 1, p. 31-38. 1917. 
4 Lovett, A. L., and Fulton, B. B. fruit grower’s handbook of apple and pear insects. Oreg. 
Agr. Exp. Sta. Circ. 22, p. 8. 1920. 
Journal of Agricultural Research, 
Washington, D. C. 
acr 
Vol. XXIII, No. 1a 
Mar. 24,1923 
Key No. Oreg.-8 
(969) 
