TIME OF ACTIVITY 435 



strong wind but remain hidden away at times when such wind 

 storms occur. Some mosquitoes are able to resist moderate winds, 

 but nearly always fly against them instead of with them. The salt 

 marsh mosquitoes are apparently an exception to the sedentary 

 nature of mosquitoes, as shown by Smith's work in New Jersey. 

 These mosquitoes commonly migrate for a number of miles and 

 may go as much as 40 miles inland from the salt marshes which 

 bred them. The common salt marsh mosquito, Aedes sollidtans 

 (Fig. 188), the mosquito that made New Jersey famous, breeds in 

 enormous numbers in the extensive coastal marshes of New 

 Jersey, whence it migrates inland, and sometimes crosses the 

 Hudson River and invades New York City in hordes. The 

 author has seen mosquitoes (not positively identified as this 

 species) literally in clouds on the roofs of buildings in the down- 

 town section of New York, where the day before not a mosquito 

 was to be found. With the exception of a few of the salt marsh 

 species, however, an abundance of mosquitoes can almost al- 

 ways be looked upon as evidence of the existence of breeding 

 places within a mile, and usually within a few hundred yards. 



Although most species are not migratory, railroad trains, 

 street cars, ships and other conveyances are efficient means of 

 transfer for mosquitoes. Hawaii is said to have been free of 

 these pests until they were introduced with sailing vessels, in 

 which mosquitoes can usually find plenty of water for breeding. 

 The great number of trains daily running inland in New Jersey 

 from the. marsh-studded coast is undoubtedly a factor in keeping 

 more distant suburban towns stocked. Well established cases 

 are on record of places once free of mosquitoes becoming infested 

 after the advent of railroad train or boat service. 



Time of Activity. Although mosquitoes are usually looked 

 upon as strictly nocturnal, and though this is true of most of 

 the common species of temperate climates, it is by no means 

 characteristic of the whole group. Many species, including all 

 Anopheles, are active chiefly at twilight, in the evening, or early 

 morning. Knab found that the mosquitoes of northern prairies, 

 where the nights are too cold for them, are active throughout the 

 day only. A large proportion of forest-living tropical species, 

 at least in America, are said to be diurnal. Some of the mos- 

 quitoes of the northern woods are apparently ready to bite 

 when a victim approaches, whether it be day or night. The 



