August, ’23] 
CONNOR & MONROE: KILLING STEGOMVIA LARVAE 
381 
from the air could easily be determined. This was done in our labora¬ 
tory by filling a bottle completely full of water containing larvae, then 
placing the thumb over the top to prevent the admission of air, and 
inverting the bottle in a larger jar of water much as is done in fashioning 
a home-made barometer. The larvae, thus prevented from obtaining 
any oxygen whatsoever except what they might get from the water 
itself, died in from three and one-half to thirty-six hours. A good film 
of kerosene, however, had been found to kill all but a very small per 
cent of larvae in from 60 to 100 minutes, though an occasional small 
larva was known to have lived under an oil film for as long as three days. 
Recently many experimenters have come to believe that kerosene 
acts upon larvae not only mechanically by excluding the supply of free 
oxygen, but also as a poison showing a selective action on the epithelium 
lining the inside of the air siphon. If this is true, only a short exposure 
of the larvae to the coating of oil should be necessary for their elimination 
and the inspectors may safely permit the washerwomen to remove the 
oil from lejia in much less time than one hour. 
In order to determine the length of time larvae survive under an oil 
film, a series of four experiments was conducted. In the first of these, 
six wide-mouthed bottles were set up in the laboratory and nearly 
filled with water. Twenty larvae were placed in each bottle, and a 
thick layer of kerosene was applied to the surface of the water. After 
periods varying from one-fourth to one and one-half hours, the kerosene 
was decanted and completely removed by adding water until the bottle 
had overflowed for some minutes. The kerosene in two of the bottles 
was allowed to remain, thus serving as a check to determine the length 
of time required for the film of kerosene to kill the larvae. Results of 
this experiment are shown in Table 1. 
It was seen that larvae could be destroyed by a much shorter ex¬ 
posure to the action of the oil than was employed in the foregoing ex¬ 
periment, for in all the bottles from which the oil was removed the larvae 
died nearly as soon as those in the check bottles. Only one exception 
occurred: in bottle 5, one iarva recovered entirely and did not seem to 
be injured at all by an hour’s exposure to the oil. In view of the fact 
that the other fifty-nine larvae were destroyed by the same or shorter 
contact with the oil, it may be assumed that either this larva had re¬ 
mained at the bottom of the bottle, subsisting on stored up oxygen or 
extracting the needed oxygen from the water by means of its anal gills, 
or else had for some reason remained refractory to the action of the 
poison. It would seem that the presence of a single larve in lejia or in 
