Pomona College Journal of Entomology 689 



known. It is (|iiitr proh.-ihlf, liowt-vcr, tli.'it c.-ircf'ul siarcli will rcvf.'il tlit-ni in 

 many otlitr localitiis. 



As nicnlioiiid in tlic resume of Dr. Ilow.-ird's articl<-, tlie Hy, I'silopii 

 petrolri ("()<|., lielonfjs to tlie lainily Ephydridae (Diptera), all the iiieini)ers of 

 wliicli arc more or less swb.Kjuatic in the larval .stage and live in all sorts of 

 peculiar and unexpected ))laces, such as brackisli water of all kinds, slime and 

 ooze, human urine and excrement, etc. 



The method of ovijjosition is as yet unknown, but in all probability the egu; 

 are deposited on the soil or sticks or leaves close to the ])etroleum pools, and tlie 

 larvae on hatchinff iunnediately find their way into the oil. It scarcely seems pos- 

 sible that oviposition is on or in the oil itself. However that may be, I have 

 found exceedingly minute larva?, scarcely more than one or two millimeters in 

 length, swimming about in the petroleum. 



The swinnning, if it may be called such, is very slow and resembles closely 

 the movements of any maggots in liquified carrion or decaying fruit. The larva 

 usually remains and moves about near or on the surface of the oil, although fre- 

 quently it goes entirely mider the surface for a considerable length of time. In 

 fact the specimens which were sent to me by Professor Esterle}' came in a small 

 bottle half full of petroleum and were more than twenty-four hours in transit 

 before they were ojjcncd in the laboratory here. Many of them were at the 

 bottom of the bottle and still alive and active when transferred to a shallow dish 

 of petroleum. The explanation of the possibility of this will appear soon. 



In watching the habits of the larva it was noted that when one, in swim- 

 ming about in the dish, came to the edge of the oil it iunnediately turned back 

 towards the center of the dish. Some were found, however, to leave the oil 

 and crawl off across the table. These soon became clean, without oil clinging to 

 them, and a little later seemed to be drying up. A few hours after their emer- 

 gence from the oil they became almost motionless, apparently ver}' weak, and 

 more or less shrivelled and dried. Death followed in twelve to eighteen hours. 

 The cause of death is probably two-fold ; no opportunity of getting food when 

 removed from the oil, and the drying of the body tissue when not protected by 

 the petroleum. 



I do not know how many days or weeks the larva lives, but when it attains 

 the length of seven to ten millimeters, it crawls out of the oil to pupate. The 

 pu))ating habits in its native haunts have not been determined yet, but in the 

 laboratory it pupates in various places outside of the oil, such as on the cover of 

 the cage as noted by Dr. Howard, or on the table surface within the confining 

 bell-jar as I found. In one dish I placed a little soil which soon became sat- 

 urated ; also a small cork an inch long was placed in it. No pupse were found 

 outside the dish, so it would seem that pupation took place either in or on the 

 soil, though none was found there. Two pupce were found in the small cavities 

 of the cork, but there were several adults that emerged from this one dish, show- 

 ing that ))upation must have occurred somewhere else, also. These facts, how- 

 ever, throw but little light on the natural liabits, and these habits must be de- 

 termined by aetu.il field observation. Probably pupation takes place in the oily 



