Pomona (college Journal of rLntomology 



Volume W M A ^ 1 'M 2 Niiml)iT 2 



Tllli FETROLEl M 1 LV IN CALIIOK.MA 



Psilopa petroici (^oq. 



I). I.. ( KAU Kdlll) 

 STANFOIll) IMVEHSITV, CAMKOHMA 



Th.it criuii- |)(triiltiiiii. so coiist.iiitly iixcl as n vi-ry i-tTcrtivc iiisfctiriilr. 

 should he the linhitat in wliicli an inscj't passes its larval existence, seems ve-ry 

 remarkable, to sny the least. Yet such is exactly the case. The larva of an 

 Kphydrid Hy 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 nothiii); of its ai)parent preference for it to other 

 nu'din, at once demands our closest attention in ordi-r to determine liotr the 

 or^raiiism exists therein. What special modification in adaptation, structure and 

 physiology to fit it for succi'ssful life in its unusual life conditions does it 

 possess ? 



It is till- purpose of tlii> study to show the cxtern.-il .10(1 intirnal anatomy 

 particul.arly in relation to its ad.iptation for its life, and, also, to determine the 

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

 the oil itself. 



Not beinjf where 1 could have .leeess to .-my of the oil-fields and see thi- 

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

 itations attendant to the scanty numbers of larvip 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 nu' many live specimens for study, is studying 

 the reactions to various stinuili and their life-liabits. so that my jiaper need not 

 go into that ))hase at all. I wish here to acknowledge with hearty thanks the 

 assistance rendered to me in this study by Dr. V. I.. 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 tliis University, who 

 is responsible for the facts herein related to nutrition. 



The adult and larva have been known to scii-nce for only :i comparatively 

 short time, having been described by Co(|uillet in 18<)9 (C.inad. Ent.. Vol. XXXI. 

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

 colored, (iruinose exci'pf the lower part of the occiput, cheeks and sides of f.ace. 

 whieli are thinly grayish pruinose; h:ilter<'s yellowish, the knobs white. Eyes 

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

 slighlly longer tli.m second, the spines of the latter not reaching Ixyond the 

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



