50 Proceedings of Ninth Annual Meeting 



tion might be obtained. Again unfortunately this is impractical 

 because of the immense number of people concerned and the 

 unwillingness of the average man to take the time and trouble to 

 express an intelligent judgment. 



The second method is to make mosquito collections. Unfor- 

 tunately variable factors, such as mosquito habits, air movements, 

 atmospheric moisture, temperature, light, precipitation, elevation, 

 plant growth, difference in collectors as regards activity, methods 

 and attractiveness to mosquitoes, are extremely difficult to elim- 

 inate or even to evaluate. Certain efforts have been made in the 

 direction of eliminating or evaluating or both of these numerous 

 variable factors. 



THE VARIABEES IN MOSQUITO C0LI.ECTI0NS THAT MUST BE 

 ELIMINATED OR EVALUATED. 



All common species other than Anopheles quadrimaculatus ap- 

 parently are most active during a period beginning at dusk and 

 ending about 9 o'clock, standard time. The common salt marsh 

 species, such as cantator, sollicitans and taeniorhynchus, fly and* 

 bite vigorously during the day, and the same may be said of the 

 common fresh water swamp mosquito sylvestris. On the other 

 hand, the salt marsh mosquito salinarim, the house mosquito 

 pipiem, the secondary fresh water swamp mosquito perturbans^ 

 the woodland pool mosquitoes stimulans and canadensis, are 

 troublesome almost exclusively in the period first mentioned. 

 Anopheles punctipennis is commonly troublesome in the evening, 

 while quadrimaculatus is apparently rarely so. What time during 

 the night quadrimaculatus attacks most vigorously is not well 

 known. With these differences of habit in mind, it is obvious 

 that where collections of the three chief salt marsh forms and of 

 the primary salt water swamp form can be made during the day 

 under favorable conditions, the collections of the house mosquito, 

 woodland pool mosquitoes, salinarius and punctipennis, must be 

 made during the evening, between the oncoming of dusk and 

 about 9 o'clock. Collections of quadrimaculatus must be made 

 within the houses or shelter, and not in the open. 



It is a well-known fact that a breeze exceeding 10 miles an hour 

 causes the mosquitoes to cling to vegetation and prevents them 

 from being troublesome, and that either still air or wind not 

 exceeding 5 miles an hour is most favorable for mosquito activity. 

 Furthermore, it is well known that while an atmospheric moisture 

 between 70 and 96 per cent, is most favorable to the mosquito's 

 activity, actual precipitation renders them inactive and not trou- 

 blesome. Furthermore, it is also well known that while a tern- 



