POLS] Behavior of Anopheles 239 
of all, food. While it is true it does not increase in size after 
emergence excepting as food or eggs swell the abdomen, it does 
seem that the reproductive organs need further growth, and for 
this food must be taken. But since the preservation of the 
species becomes a powerful factor at work within the animal, 
so starvation and captivity may cause a hurried development 
of ova. In his dissection of gravid typhoid flies, the writer 
found more ova in flies which had been fed after emergence 
from the puparium than in flies totally deprived of food. 
The drastic anti-malarial measures of man place him a 
powerful agent of destruction at work in the environment. 
Man as an agent hastens or retards natural processes. Thus 
by means of a ditch and a pipe-line dredge, he has driven the 
mosquito from its paradise and made its return thereto 
impossible. 
III. Historic Factors. 
The creation of the salt-marsh habitat can be traced to the 
work of the old French Canal Company, as already described. 
When Americans built the big Gatun dam and made the 
Spillway, they did more than impound the waters of the Chagres. 
They changed the drainage, tamed the river which often came 
down in flooding proportions, and by allowing it to peacefully 
flow past the new Spillway, did away with the annual floods. 
The floods eliminated, and the increased rainfall in December, 
1912, were the prime factors which prepared the marsh for 
extensive breeding. 
B. DYNAMICS OF THE ENVIRONMENT. 
I. The Habitat of the Immature Stages. 
Larve and pupe were found most frequently associated with 
green alge, which plants afford them ample shelter, support 
and fair protection from fish and larve of carnivorous insects. 
The respiratory tubes of the larve were often noted in close 
proximity to the bubbles of oxygen given off by the alge. 
Experimentally, young larve (2d moult) were sealed hermet- 
ically in a glass jar containing filtered water from the marsh 
and a small quantity of living alge; the larve developed into 
adults. Out of the ten larve originally placed in the jar, three 
adults ensued. The time duration was almost twice that under: 
