THE YELLOW-FEVER MOSQUITO. 11 
larve under observation the development was hastened until the 
life cycle was completed in from six to eight days. 
DURATION OF EARLY STAGES. 
Temperature has the greatest influence, not only upon the hatching 
of the eggs but, also upon the subsequent development of the larve. 
The effects of various temperatures on the early stages were care- 
fully investigated by the American commission in Cuba and by the 
French commission in Rio de Janeiro, and the results of both agree 
very closely. The shortest period of development to imago observed 
-by Reed and Carroll during summer weather in Cuba was 93 days, 
divided as follows: Incubation, 2 days; larval stage, 6 days; pupal 
stage (fig. 6), 36 hours. This, how- 
ever, was believed to be exceptional. 
In average summer, temperature the 
time required for the complete meta- 
morphosis ranges ordinarily from 11 
to 18 days. The French observers in 
Rio de Janeiro found that the most 
favorable season for rapid develop- 
ment was when the night tempera- 
tures ran from 79° to 81° F. and the 
day temperatures from 82° to 88° F. 
They found that some of the larve 
of this mosquito reached the pupal 
stage seven days after the hatching 
of the eggs, and the adult condition fic. 6.—The yellow-fever mosquito : 
on the ninth day, and that generally Pupa. Much enlarged. (Original.) 
most of the larve from the same laying of eggs produced imagoes 
about the tenth day. 
RESISTANCE OF LARVZ TO ADVERSE CONDITIONS. 
Larve of the yellow-fever mosquito have been found in nature in 
brackish water containing 35 per cent of sea water. With 40 per 
cent sea water the larve still survived and produced imagoes. Ex- 
periments have shown that the larve may in nature survive in water 
which, through evaporation, has reached a high degree of salinity, 
and if afterwards, through rains, the water becomes again diluted, 
the larve may develop to imagoes. 
The degree of resistance to desiccation of both larve and pupe is 
important from the practical standpoint. The first yellow-fever com- 
mission to Vera Cruz found that in’ that dry climate larve died 
quickly when the water containing them was poured on the ground. 
In moist climates the larve may, under favorable circumstances, live 
547 
