224. MOSQUITOES OF NORTH AMERICA 
season, when all other breeding-places, artificial and natural, have ceased to 
exist.” 
ANOPHELES BREEDING IN SEA-WATER. 
We have mentioned above a statement by Smith that Anopheles has been 
found in the salt marshes, and this observation has been repeated by others. 
Anopheles have been found breeding in salt or brackish water in many parts of 
the world; in every case the habit has been found restricted to certain species. 
An article was published by Dr. W. T. de Vogel, health officer of Samarang, 
Java, in the Atti della Societa per gli Studi della Malaria for 1907, bearing 
upon upon this question, and his observations are so important that we devote 
considerable attention to them. De Vogel found that the investigations of 
several Italian workers have negatived the idea that Anopheles can multiply in 
pure sea-water and that they have shown that the maximum proportion of 
sodium chloride in the water which Anopheles larve can stand is 1.87 per cent 
according to Perrone, and 1.75 per cent according to Vivante. De Vogel, 
having made some elaborate studies in regard to malaria at Samarang, found 
as early as 1902 that Anopheles was breeding in a certain pool containing 2.8 
per cent of chloride of sodium. Later he verified these results in several in- 
teresting cases. One of these was the island of Onrust, a small coral island 
situated two thousand meters from the mainland, and which contains no fresh 
water whatever. The distance from the mainland is such that even if Anopheles 
were brought from the mainland by winds they would not be numerous enough 
to cause trouble. Nevertheless a marine station established on the island had 
to be abandoned on account of the ravages of malaria among the workmen and 
Dr. de Vogel believed that this was due to Anopheles breeding in the sea-water 
upon the island itself. 
De Vogel studied also the conditions in the Karimon Islands, a little archi- 
pelago in the Java Sea, sixty-five kilometers from the coast. The first colonists 
in this archipelago were convicts and were sent there to cut down the forests of 
rhizopores. There were no buildings, and the convicts were forced to sleep on 
the earth. The mortality was between two and three thousand in two years. 
Later one of the officers named von Michalofski—a plain man but full of good 
sense—succeeded in putting a stop to the excessive mortality by drying the sea- 
water pools, removing a part of the forest, and raising the ground on which the 
men slept. The success which followed these measures leads de Vogel to sup- 
pose that the mortality had been caused by malaria, and this supposition is all 
the more probable since, as he himself has verified, malaria is today rife among 
the population of the islands. 
There is on the island of Grand Marimon only a single permanent source of 
fresh water which has only one restricted outlet. During the dry season there is 
no mingling of fresh water with sea-water, so there exist during that season 
many pools of dead sea-water peopled with Anopheles larve ; these pools contain 
not less than three per cent of sodium chloride and must then be considered as 
concentrated sea-water. 
