14 

 important, as loud sounds tend to repel mosquitoes in flight and will not activate 



mosquito flight. The benefit of sound attraction is that it can attract many male 



mosquitoes in a relatively short period of time. For example, 80% of caged male 



Ae. aegypti were attracted within 5 s [8]. Doppler frequency shifts have been shown 



to have little effect upon attraction. 



Chemical attractants 



The search for attractants may identify single attractants for specific species; 

 however, a universal mixture to attract a wide range of species is sought. Certain 

 combinations of chemicals may synergistically attract species more than others [5.20- 

 23]. As with heat, some evidence exists that responses to volatile attractants and 

 carbon dioxide may be tonic or phasic. In a constant (tonic) emission of attractants 

 and/or carbon dioxide, mosquito response was found to decrease within minutes 

 [7,17]. 



Airborne chemical attractants are carried by wind producing a series of 

 plumes of host odor [9]. These plumes are neither uniform in size or distribution, 

 thus eliciting a phasic rather than tonic response by mosquitoes. As previously 

 mentioned, mosquitoes fly upwind in a zig-zag pattern, constantly adjusting to fly 

 upstream into the plumes. The turning readjustment increases as mosquitoes near 

 the host or source due to increased plume rate as well as decreased plume size. 

 Odor plumes alert mosquitoes; however, visual cues provide better means for long- 

 range attraction. 



