586 Cuig Pine 
In addition to the natural materials selected by the larvae, different 
kinds of foreign food — foods not found in their natural habitat — were. 
used to learn what kind of plant materials would serve as the most favor- 
able food to them. The water taken from the pools was filtered in 
order to eLminate any natural food. The four kinds of foreign food — 
(1) cornmeal, (2) green grass, (3) broad leaf plantain, and (4) alfalfa 
meal—were placed respectively in four aquaria. Each aquarium had five 
larvae measuring from 7 to 8 millimeters in length. After five days the 
larvee in the first two aquaria all died. After two weeks, two pupae were 
found in each of the other two aquaria. At the end of three weeks, three 
adults and one pupa were found in the fourth aquarium with the alfalfa 
meal in the water. 
Respiration 
In respiration the larva sticks out its caudal process to indent the 
_ surface film. The spiracle membranes flatten out on the water surface, 
resembling the leaves of Marsilea, and the spiracles open to the air. 
Meanwhile the larva is feeding on plancton organisms, as indicated 
by the frequent moving of its mouth parts. After a while it withdraws 
its caudal tips from the surface film. It often requires considerable effort 
for the larva to pull them down into the water. Frequently the larva 
hangs suspended close underneath the surface, swinging its body back and 
forth trying to overcome the adhesion between the caudal tips and the 
surface film. The grown larva is able to relieve itself sooner or later, but 
to a comparatively young larva this attachment is a constant source of 
peril. On one occasion the writer found five young larvae, holding one 
another together with their last prolegs, hanging below the surface help- 
lessly. In failing to swim they all died about a day later. The writer 
corked an eight-ounce bottle completely filled with salt water in which 
were a few larvae. A large air bubble was unavoidably left on the under 
surface of the cork in contact with the water. After five or six hours 
most of the larvae came up, getting around that large bubble, and remained 
there until they pupated. At another time several larvae were screened 
at the bottom of an aquarium, a piece of wire gauze being placed half- 
way between top and bottom; the larvae thus barred from reaching the 
surface were suffocated. 
