Annals E?itomological Society of America [Vol. VI, 



A. GENERAL CONSIDERATION. 



Dispersal includes everything involved in the movements of 

 animals from one place to another. It is a more or less eccentric 

 movement because the paths taken are usually those of least 

 resistence and economy. In mosquitos, dispersal is limited to 

 four general means: (1) flight of the adult, (2) the adults may 

 be carried by the wind, (3) they may be carried in trains, other 

 vehicles, on the clothing of man or on other animals, and (4) the 

 eggs, larvae, pupas and to some extent the adults, may be carried 

 down stream or across a pond by current or wind action. 



Such mosquitos as transmit diseases to man, especially 

 when they serve as intermediary hosts in such transmission, 

 are usually limited in their breeding area to the vicinity of 

 human habitations. This is well illustrated by Aedes calopiis 

 Meigen which transmits yellow fever, and Anopheles albimanus 

 Wiedemann, responsible for E. A. malaria. Such mosquitos 

 (verified by us in the two cited species) are not distant travellers, 

 and if they do come from distant places, it is through gradual 

 infiltration. Some species of Culex are powerful fliers; others 

 apparantly remain only near their breeding place. 



To merely liberate colored adults is almost futile. The 

 study is an ecological one and requires a knowledge of all the 

 physical, biotic and historic factors that in any way enter into 

 the environment of the species studied. The statements given 

 under the three subheads following are not intended to be 

 exhaustive, and they must be amplified according to the species 

 selected. 



1. Physical Factors. 



A good map of the region selected for experimentation is 

 necessary. It must indicate with fair accuracy the topography, 

 commercial projects, habitations, streets, roads, and inlets of 

 oils or poisonous refuse into streams or ponds and the extent 

 of this pollution. 



A recording anemometer should be in operation at the central 

 station, and in addition to the velocity per hour intervals, 

 should give the eight main directions. If more than one such 

 instrument is available, the others may be distributed at stations 

 where decided wind deviations take place. Small portable 

 anemometers will greatly augment the data. A self-recording 

 rain guage is a valuable addition. 



