Pomona (college Journal of rLntomology 



Volume IV MAY 1912 Number 2 



THE PETROLEUM FLY IN CALIFORNIA 



Psilopa petrolei Coq. 



D. L. CRAWFORD 

 STANFORD UNIVERSITY, CALIFORNIA 



That crude petroleum, so constantly used as a very effective insecticide, 

 should be the habitat in wliieh an insect jjasses its larval existence, seems very 

 remarkable, to say the least. Yet such is exactly the Case. The larva of an 

 Ephydrid fly lives, feeds, and swims about in the pools of crude petroleum which 

 are so numerous in the various oil-fields of California. That any animal could 

 exist in such a medium, to say nothing of its apparent preference for it to other 

 media, at once demands our closest attention in order to determine how the 

 organism exists therein. What special modification in adaptation, structure and 

 physiology to fit it for successful life in its unusual life conditions does it 

 possess } 



It is the i)ur))ose of this study to show the external and internal anatomy 

 particularly in relation to its adaptation for its life, and, also, to determine the 

 facts of nutrition and protection against the protoplasmic poisons which are in 

 the oil itself. 



Not being where I could have access to any of the oil-fields and see the 

 larva? and adults in their natural conditions, and because of the necessary lim- 

 itations attendant to the scanty numbers of larvae at my disposal and the un- 

 natural surroundings in which they must be placed, it is not possible to give 

 here many facts of their life-history. Dr. C. O. Esterley of Occidental College, 

 to whom I am indebted for sending me many live specimens for study, is studying 

 the reactions to various stimuli and their life-habits, so that my paper need not 

 go into that phase at all. I wish here to acknowledge with heartj' thanks the 

 assistance rendered to me in this study by Dr. V. L. Kellogg of the Department 

 of Entomology, under whose supervision this study has been made, and to Prof. 

 Robert E. Swain, Professor of Physiological Chemistry in this University, who 

 is responsible for the facts herein related to nutrition. 



The adult and larva have been known to science for only a comparatively 

 short time, having been described by Coquillet in 1899 (Canad. Ent., Vol. XXXI, 

 p. 8). This original description is as follows: "Black, polished, not light 

 colored, pruinose except the lower part of the occiput, cheeks and sides of face, 

 which are thinly grayish pruinose ; halteres yellowish, the knobs white. Eyes 

 densely hairy, most approximate at middle of face. Third joint of antennae 

 slightly longer than second, the spines of the latter not reaching beyond the 

 apex of antennsB. Wings hyaline, tinged with gray on nearly the costal half, 



