582 Cutn PING 
and died. The average room temperature was the same as that in 
Experiment I. 
Experiment IIT.— Four eggs were placed in salt water. After one day 
one of them hatched and the larva measured 1 to 1.5 millimeters; later 
on the same date the remaining three eggs hatched and on the fifth day 
the larvae averaged from 4 to 5 millimeters in length; after seven days 
they averaged from 7 to 8 millimeters; after eleven days one larva 
measured 10 millimeters, a second one measured 9 millimeters, and 
the other two measured from 8 to 9 millimeters and at this time 
pupated. On the thirteenth day the other two pupated. The average 
room temperature was the same as that used in Experiments I and II. 
Experiment IV.— Four eggs from two to three days old were placed in 
fresh water. After one day two of them hatched; after four days these 
two larvae measured from 2 to 2.5 millimeters each; after five days one 
measured 3 millimeters, and the other 4 millimeters; after seven days the 
other larvae, which hatched out much later, averaged 2.5 millimeters 
each; the one which measured 4 millimeters on the fifth day died. All 
the others died on the thirteenth day. The average room temperature 
was the same as that in the first three experiments. 
In a comparison of the results of the above experiments, the striking 
difference in the development of the larvae in the fresh and in the salt 
water may at once be seen. None of the larvae could grow well and 
attain pupation in the fresh water with the total absence of salt, although 
other conditions were equal. The larval stage in salt water, under the 
conditions previously stated, lasted from eleven to thirteen days. The 
pupation took place much earlier than usual, when the larva was only 
from 8 to 9 millimeters long. This was, perhaps, due to the more even 
temperature or other artificial conditions maintained in the laboratory. 
Habits 
Locomotion 
The larvae are always found in still and stagnant water. Their 
modes of locomotion, under normal conditions, show their adaptation to 
such environments. First of all, the larvae are slow in movement, 
never darting nor Jumping with appreciable speed; in the second place, 
they are awkward in directing themselves forward and turning them- 
selves around, never exhibiting any energetic directness. And finally, 
the larvae, especially when reaching maturity, prefer to remain still on 
