RESISTANCE TO DESICCATION 291 
hastens the hatching of the eggs, and of Jennings who has noted larve in 
water containing wood ashes. In this latter case, at Cartagena in Colombia, the 
larve were found in large numbers in an earthen pot containing a large quantity 
of wood ashes in brackish water from a shallow well near the sea-coast. None of 
the larvee produced imagos. In such cases the potash contents, which are 
variable with different kinds of wood, must be taken into account and also the 
fact, already pointed out, that after some time the water loses its alkalinity. 
The degree of resistance to desiccation of the larve and pup of Aédes calopus 
is important from the practical standpoint. The first yellow-fever commission 
to Vera Cruz found that in that dry climate larve died very quickly when the 
water containing them was poured upon the ground. In moister climates the 
larve may, under favorable circumstances, live out of water a considerable time 
and the pupex show great resistance to desiccation. 
Peryassti records a series of experiments conducted on a large scale at Rio de 
Janeiro. Placed upon filter paper none of the larve lived nine hours. When 
placed upon the moist ground, according to temperature and evaporation, they 
survived as much as 13 days, and, when again put in water, developed to imagos. 
In the experiments with larve and pupe the following method was employed. 
A determined number of larve or pup were put in a watch glass with a little 
water and then emptied upon a cone of filter paper; this latter was then placed 
upon two other layers of filter paper, to absorb all the water from the first ; then, 
when the necessary time had passed, the paper with the larve was placed in a 
glass of water so that the number of dead or surviving larve could be deter- 
mined, as well as the time they required to return to a normal state. Tabula- 
tions of the results are given and from these the following data are extracted. 
Larvee dried up to three hours developed normally when returned to the water 
and it is only beyond this that they began to suffer. In the course of the many _ 
experiments the longest periods during which calopus larve survived were in 
one case 8 hours and 20 minutes, and in another 8 hours and 55 minutes. It 
must be noted that on the day on which these results were obtained it rained 
copiously all day; the evaporation, in the shade, was 1.4 mm. and the relative 
humidity 86.1. These results are based upon 64 experiments with 3685 larve. 
The larvee, when returned to the water, sometimes immediately resume their 
activity, but most of them remain immovable for from 5 to 15 minutes. Gen- 
erally the larve that did not recover within this time would die. Drying during 
periods of from three hours to four hours and fifty minutes was survived by 
from 72 to 98 per cent of the larve, and the number of these that reached the 
imago state varied from 1.5 to 75 per cent. The time to transformation, after 
being returned to the water, varied from 3 to 41 days. Experiments with drying 
during 5 hours to 6 hours and 50 minutes gave the following results: The larve 
survived in the proportion of 7.5 to 95.5 per cent; they produced imagos in from 
2.5 to 62.5 per cent. The period to transformation varied from 3 to 42 days. 
Experiments with drying for from 7% to 9 hours resulted as follows; the larve 
survived in the proportion of from 4 to 97.77 per cent and produced imagos in 
from 1.25 to 26.66 per cent; the variation in the time to transformation varied 
20 
