54 
PROPHYLAXIS OF MALARIA. 
Whatever the position of a mosquito, it can always be determined 
whether it is an anopheline by attention to the relative position 
of the proboscis to the body. In the Anophelince the, proboscis is 
always in a direct line with the rest of the body when the insect is 
resting upon a surface, while in all other mosquitoes the proboscis 
forms an angle with the abdomen. This peculiarity is easily recog¬ 
nized and gives the anopheline a distinctly “business-like" appear¬ 
ance, the entire body of the insect resembling a boring instrument. 
Practical points in the differentiation of the Anophelince. —The fol¬ 
lowing practical points may prove of use in the differentiation of 
anophelines from other mosquitoes in their various stages of develop¬ 
ment : 
1. The ova. —The ova of the Anophelince are hever found in 
masses, but are laid single upon the surface of the water, the ends 
often being connected, thus forming geometrical patterns. They are 
further distinguished by the possession of lateral “floats," which 
never appear on the ova of other mosquitoes. 
2. The larvae. —The larvae of the Anophelince are easily distin¬ 
guished from those of other mosquitoes by the absence of the long 
respiratory tube or siphon. Because of this the anopheline larva is 
compelled to lie parallel with the surface of the water, while other 
mosquito larvae hang head downward at an acute angle with the 
surface of the water. In addition the small, narrow head of the 
anopheline larva distinguishes it from other mosquito larvae. 
3. The imago or adult. —The following points distinguish the 
adult anopheline from other adult mosquitoes: 
a. The relative length of the palpi and the proboscis. —In the 
Anophelince the palpi of the female are as long as the proboscis, 
while in other mosquitoes the palpi are much shorter than the pro¬ 
boscis. The males are distinguished from the females bv their 
plumose palpi. By attention to this simple detail any mosquito may 
at once be placed so far as its relation to the Anophelince is concerned. 
b. The angle of the proboscis with the body. —The proboscis in 
the anophelines never forms an angle with the rest of the body but 
continues in a direct line with it, as already stated. 
c. The resting position. —When resting upon a surface most of the 
Anophelince form a distinct angle with the surface, while other mos¬ 
quitoes appear humpbacked owing to the fact that the abdomen is 
nearer the surface than the thorax. 
cl. The spotted wings. —Most of the Anophelince have spotted wings 
and while some other mosquitoes also present spots upon these struc¬ 
tures it is a good practical rule to always regard with suspicion any 
mosquito having spotted wings, as the chances are altogether in 
favor of its being an anopheline. 
