510 



PROTOZOA 



ance of the body holds good in the case of these protozoa is uncertain. 

 Studies made by me on over fifty birds infected with proteosoma showed 

 that (1) young birds invariably became infected, while old ones rarely 

 did ; (2) objective symptoms in young birds were much more pronounced 

 than in previously healthy older birds; (3) old birds whose resistance 

 appeared to be lowered by disease were readily infected ; (4) reinfection 

 of all birds appeared to be negative. 



The Malaria-carrying Mosquito (Anopheles). Only generalities can 

 here be considered. The common mosquito, often day-flying, belongs 

 to the culicidae; it cannot carry human malaria. It is distinguished 



FIG. 155 



Culex. 



Anopheles. 



Anopheles. 



Culex. 



(From Doflein.) 



from its night-flying or dusk-flying relative by its assuming a different 

 posture on the perpendicular wall. While the culex holds the body 

 more or less parallel with the surface, the body of the anopheles stands 

 off at a marked angle. 



Wings of culicidae are unspotted; those of Anopheles macullpennis 

 and Anopheles punctipennis are spotted. 



The proboscis of anopheles points toward the resting surface, while 

 that of culex does not do so. 



Anopheles varieties bite usually in the early evening, while those 

 of culex bite almost at any hour. * 



