NATURE OF LARVAL FOOD 287 
The first yellow-fever commission to Vera Cruz found that, on account of 
this habit, the larve are not easily disposed of by pouring out the contents of a 
barrel. ‘“ When the barrel or other container with thousands of larve is ap- 
proached and slightly agitated, the insects disappear rapidly to the very bottom, 
so that nearly all the water can be dipped from the barrel without removing 
more than a few of the larve. The barrel may be turned upon its side, and it will 
be found that about 80 per cent of the larve will stay in the few remaining 
ounces of water.” 
FOOD-HABITS OF THE LARVA. 
It has been pointed out that the larva occur most frequently in the clear 
water in rain-water barrels or in drinking-water receptacles in houses. The 
water in such receptacles contains more or less animal matter, such as particles 
of human skin or remains of insects, as well as vegetable refuse, and such 
probably is generally the food of the larvee. The larve feed at the bottom, where 
they mouth over the organic sediment, even when the water is very deep. Larve 
in confinement may be observed chewing vigorously at dead insects or larval and 
pupal exuvie. 
C. 8. Banks has observed the larve in the Philippines and says: ‘“ They feed 
largely upon the sediment contained in the dregs, which may be both animal 
and vegetable in its character, but more frequently vegetable, as it is composed 
of the bits of decaying nipa forming the roofs from which the rain water is 
collected. The larve, in feeding, move forward over the bottom of the vessel, 
taking in the particles of food with great rapidity and rejecting tiny morsels of 
undesirable material in a constant stream.” 
Goeldi found that the larvee of calopus are cannibalistic, and this has been 
confirmed by the Brazilian observers at Rio de Janeiro, who state that the larger 
larve devour the smaller ones. This habit probably accounts for the develop- 
ment of the larve in very clear water, which has been so frequently noted. 
An interesting fact is that the growth of these larve is greatly hastened by the 
presence of a small amount of fecal matter in the water. Reed and Carroll, at 
Havana, found that calopus bred in the tin cans used for carrying away human 
excrement and throve remarkably under those circumstances. 
Dupree and Morgan, of Baton Rouge, have also recorded the fact that by 
adding fecal matter to the water they hastened the development until the life- 
cycle was completed “in from six to eight days.” 
The French commission to Rio de Janeiro found that the larve develop in 
clear water, but also thrive in foul water. Water containing alimentary debris, 
amylaceous or fatty material seems to suit them perfectly. These investigators 
thought that rain water, on account of the microbes which it contains, seems to 
be more favorable to their development than spring water. In the laboratory the 
larvee were easily reared in water in which had been placed excremental pellets, 
or grains of corn or wheat. They seemed to be less at ease in muddy water and 
in water containing macerated dead leaves and vegetable debris, but they found 
that the differences in the duration of the different stages of larval evolution in 
