PROPHYLAXIS OF MALARIA. 
53 
I have already called attention to the fact that the ova of anophe- 
lines will withstand drying for some time, and I am of the opinion 
that in the Tropics many species would cease to exist were it not for 
this property, owing to the long dry season and the comparatively 
small number of hibernating females. 
As regards the number of generations during a season our knowl¬ 
edge is very incomplete. According to the observations of Kulagin 25 
the anophelines have only one generation annually. He calls atten¬ 
tion to the fact that the female anopheline does not lay her eggs all 
at one time and states that, in temperate regions, the egg-laying ex¬ 
tends throughout the entire summer, and that the adult mosquitoes 
derived from these eggs do not lay eggs until the following year. 
His observation^ extend over sev¬ 
eral years and are the most ac¬ 
curate that we possess upon this 
subject. 
Nothing is known regarding 
this subject in respect to the mos¬ 
quitoes of the Tropics. 
Resting position of adults .— 
The resting position of adult 
anophelines and the position as¬ 
sumed when biting, the two be- 
Cz 7 
ing practically identical, offers 
one of the easiest and most valu¬ 
able methods of differentiating 
between them and other mos¬ 
quitoes. When resting upon a 
flat surface, as a wall, mosquitoes 
belonging to the Anophelinaz , 
with few exceptions, form a dis¬ 
tinct angle with the surface, the 
insect resting upon the first two pairs of legs, the last pair floating in 
the air or held out straight behind it. The angle formed by the body 
of the mosquito and the surface varies, but sometimes is nearly a right 
angle. The only exceptions to this rule among the anophelines 
commonly observed is J [yzomyia ( Anopheles ) culicifacies , which 
rests upon a surface in the same position as a Culex mosquito, and 
Pyretophorus ( Anopheles) superpictus and Myzomyia ( Anopheles) 
hispaniola , which assume a perpendicular position in reference to the 
wall. 
The position assumed b}^ other mosquitoes, as Culex , Stegomyia , 
etc., is well described as u humpbacked,” the abdomen approaching 
the resting surface while the thorax is distinctly higher than any 
other portion of the body, thus giving the humped appearance. 
Fig. 3. —Comparison of resting position of 
Anopheles and Culex. 1. resting posi¬ 
tion of Culex, on vertical surface; 2, 
resting position of Anopheles on vertical 
surface. (The resting position upon a 
horizontal surface may be observed by 
turning the page so that the vertical 
line becomes horizontal.) 
