224 The Control of Mosquitoes 



sources of Anopheles at Gatun, Christobal, and 

 Colon, presented conditions that may not be 

 limited to the tropics, and afford precedents for 

 future anti-malarial work near seacoasts farther 

 north. 



Although the Anopheles is usually considered a 

 night-biting mosquito, Isthmian observation has 

 proved that some species bite people in the day- 

 time, both in houses and in forest shade; and when 

 very numerous these insects appear less afraid of 

 capture or exposure to natural light. In one 

 instance Anopheles tarsimaculata and Anopheles 

 albimanus bit freely all day in the sunlight, but 

 this was the sole exception noted during more than 

 twelve years of observation. 



Other new facts of importance ascertained and 

 improvements devised relating to control measures 

 that restdted in reducing the cost and increasing 

 the efficiency of anti-malaria work were : 



Concentrated larvacide, effective when and 

 where oiling is useless, is now made and trans- 

 ported economically. 



Practical tests were made to discover the cause 

 of the decay of copper alloy screening. It was 

 found that monel metal mosquito wire, sixteen or 

 eighteen mesh, remains intact after the best grade 

 of copper bronze wire has decayed. 



