CONDITIONS AFFECTING EGGS 281 
BREEDING HABITS. 
THE EGGS. 
The different stages of this mosquito are carefully described in the systematic 
portion of this work. The eggs, as above described, are frequently laid in small, 
irregular groups some distance above the margin of the water, and may remain 
dry for long periods, hatching when reached by the water. They develop better 
after having been dry for a period. Reed and Carroll state: 
“The resistance of stegomyia’s eggs to external influences is worthy of note. 
Drying seems to be but little injurious to their subsequent fertility. We have 
found that eggs dried on filter paper, and kept for periods of from ten to ninety 
days, will promptly hatch when again submerged in water. Dried eggs brought 
with us from Havana, in February, were easily hatched during the month of 
May, in Washington, furnished about 60 per cent. of the usual number of larve 
hatched from fresh eggs. Freezing does not destroy the fertility of the eggs. 
Although freezing with a mixture of salt and ice for thirty minutes has several 
times seemed to prevent subsequent hatching; on one occasion a batch of one 
hundred and fifty-five eggs, freshly deposited, which were frozen at a tempera- 
ture of -17° C., for one hour, then thawed out at room temperature and placed in 
the incubator at 35° C., began to hatch on the sixth day, the majority furnishing 
active larve on the eighth day. In another observation, freshly deposited eggs, 
frozen at -17° C. for half an hour on two successive days, began to hatch on the 
third day as usual at incubator temperature. The resistance of stegomyia’s 
eggs to drying for a period of three months would appear to demonstrate that 
this genus of mosquito could survive the winter in Havana, without the presence 
of hibernating females. Doubtless the genus is preserved in both ways. It is 
probable that the same could occur in our extreme southern latitudes.” 
The Brazilian investigators at Rio de Janeiro determined that the eggs will, 
when dry, preserve their vitality unimpaired for five months. Eggs placed on 
filter paper and kept in test-tubes developed after this period but beyond that 
period they failed to hatch. Francis asserts that eggs hatched which he had 
kept dry during six and a half months. Eggs sent to Theobald in England, 
from Cuba, hatched after two months and a half. Itis to be supposed that under 
natural conditions the eggs of calopus will survive out of water even longer than 
the longest period achieved experimentally. It should be remembered that in the 
majority of the species of Aédes the eggs do not hatch until the following year 
and that a percentage, with some, and we believe with many species, remains 
dormant until a second year. 
Agramonte (a member of the American commission to Cuba), in a chapter on 
mosquitoes and yellow fever appended to Berkeley’s “ Laboratory Work with 
Mosquitoes” (New York, 1902), states that the duration of the egg-state varies 
according to the season of the year, the temperature of the water and the 
chemical conditions of the water. He shows that with the lye of wood-ashes, em- 
ployed by laundresses in Cuba for the purpose of whitening the clothes, the eggs 
hatch more quickly than in the dirty water of overflows and gutters, and yet the 
latter contains more organic matter. 
The duration of the egg-stage according to Agramonte is from fifteen hours 
to three days. J. R. Taylor, of Las Animas Hospital, Havana, gives the dura- 
tion of the egg-stage as 12 to 24 hours. The first American commission to Vera 
