June, ’18] FREEBORN AND ATSATT: PETROLEUM AND MOSQUITO LARVAE 299 
Proportionally, there is more tent surface, and also volume, in a 
tall tree than a broad tree, and this is not indicated by the tape meas¬ 
urement around the tree, or by considering the tree as a fixed geometri¬ 
cal figure. 
For practical consideration, the tall tree may well show more or less 
injury at the top to insure the insects being killed at the bottom. 
President G. P. Weldon: Discussion of this paper is now in 
order. 
R. S. Woglum: From observations in the field where the trees 
were more or less severely injured at the top, I am surprised that your 
experiments showed the same killing at the top as at the center. 
H. J. Quayle: I think as a general rule there is a greater con¬ 
centration of gas at the top than at the center of the tree, but that 
point was not brought out clearly in the particular experiments in 
question. 
D. D. Sharp: I have seen some instances where the scales were 
not killed at the top of the tree, though it is a very common observa¬ 
tion that more injury occurs at the top of the tree than elsewhere. 
J. D. Neuls: In experiments in the fumigatorium, plants at the 
top of the fumigatorium seemed to be more injured than at the bottom. 
President G. P. Weldon: The next paper is on “The Effect of 
Petroleum Oils on Mosquito Larvae,” by S. B. Freeborn and R. F. 
Atsatt. 
THE EFFECTS OF PETROLEUM OILS ON MOSQUITO 
LARVAE 1 
By Stanley B. Freeborn and Rodney F. Atsatt, 
University of California, Berkeley , California 
To the layman, mosquito control immediately suggests oiling for 
since Dr. Howard’s pioneer publications on the subject in 1892, the 
literature has been flooded with recommendations for the application 
of oil in order to control mosquitoes. Very few of these accounts sug¬ 
gest what grade of oil to use or the actual effect of the oil on the larvae 
with the result that we have widely conflicting accounts of the amount 
of oil necessary to adequately control a given area, varying data on the 
time required for the oil to kill the larvae, and no thoroughly satisfac- 
1 The authors wish to acknowledge the helpful suggestions and kindly criticism of 
Prof. George P. Gray of the University of California. 
