232 MOSQUITOES OF NORTH AMERICA 
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NUMBER OF GENERATIONS. 
The general impression is that, in temperate regions, there are several genera- 
tions of Anopheles during a season and that they continue to reproduce while 
conditions are favorable. Kulagin, in Russia, appears to have been the only one 
who has investigated the question carefully and after observations through 
several years he concluded that there is but a single generation annually, the 
imagos issuing from pupe not laying eggs until the following year. It is well 
known that the female Anopheles do not lay all their eggs at one time. Accord- 
ing to Kulagin the egg-laying period is extended over the entire summer through 
the fact that some of the Anopheles do not leave their hibernation quarters until 
well into the summer. He points out that in the female Anopheles examined by 
Koschewnikow late in July all showed a strongly developed fat supply and un- 
developed ova and that the presence of the fat was a preparation for hibernation. 
We have already mentioned that in this country Smith has found the hibernat- 
ing Anopheles in similar condition. 
The observations made by Kulagin in 1906 are very convincing. In that 
year there was a very early spring in the province of Moscow; the temperature 
rose very high in April and there were no cold days. As a result of these early 
favorable conditions the hibernating mosquitoes left their shelters very promptly. 
Oviposition followed with the same promptness. He found great numbers of 
larvee about the middle of April and these developed rapidly. The imagos 
issued from the pupe during the last half of May, within a very short period. 
From the end of May on, throughout June and July no Anopheles larve could 
be found in spite of the most thorough search. Kulagin then points out that the 
conclusion is inevitable that in that year the females which issued from pupx 
about the middle of May were the ones to hibernate. 
Observations made by one of us (Knab) on the mating habits of Anopheles 
punctipennis are significant in this connection. This species has been observed 
repeatedly, swarming in the manner described on another page, but in every 
case observed this occurred well towards the end of the season. 
Further observations are necessary to determine if all the species of Anopheles 
of the temperate regions agree in the number of generations. As to the tropical 
species, practically nothing is known as to the number of generations. Quite 
probably in certain regions, where there is an abundance of water throughout the 
year, breeding is continuous. In parts of India, where there is a long, well- 
marked dry season, the behavior of the Anopheles appears to be much as in colder 
climates, only that in this case the dry time is the resting period. Stephens and 
Christophers state that in India estivating Anopheles, although they feed at 
intervals, will not deposit eggs even if suitable deposits of water are present. 
GEOGRAPHIC DISTRIBUTION OF MALARIA. 
The distribution of malaria coincides in a way with the distribution of the 
mosquitoes of the genus Anopheles; that is to say malaria does not originate in 
localities where Anopheles does not exist; but on the other hand there exist 
many localities where there are Anopheles where malaria is not to be found. 
