Species of Anopheles 51 



afraid of disturbing the specimen by close approach 

 but it was not an Anopheles. 



There is no doubt at the present time that the 

 Anopheles albimanus is responsible for practically- 

 all of the malaria transmission in the Canal Zone, 

 except at Gatun and Colon, where Anopheles 

 tarsimaculata sometimes exist in numbers large 

 enough to be of equal economic importance. The 

 decrease of malarial fever in Panama will be in 

 proportion to the eradication of these two species. 



It is now known that both species travel in 

 enormous numbers over long distances (if other 

 suitable propagation areas are not available) 

 between their place of origin and the nearby settle- 

 ments. On the Isthmus, in two instances where 

 breeding was prolific, they have been known 

 to travel from half a mile to a mile to reach houses. 

 They do not seem able to remain long in a very 

 strong light, and as a rule prefer darker places. 

 No other Isthmian mosquitoes are so persistent in 

 attempting to enter screened houses, and yet once 

 inside they seem unable to find a way out, and 

 collect on the screening soon after daylight, and 

 again at dusk. When they find they cannot get 

 out they return to the interior of the building, but 

 make another effort to pass the screened openings 

 at the same hours next day. They are seldom 



