
_ AMERICAN MUSEUM GUIDE LEAFLETS — 

quito eggs are those of the rain-barrel species—eggs which are laid 
on end, side by side, in a boat-shaped mass on the surface of the 
water in barrels, tubs, and similar places. The eggs of Anopheles are 
laid singly but frequently they float close to each other, the floating 
being favored by special structures along their sides. The larva, or 
‘“‘wriggler’’ which hatches from an egg of Anopheles has a very short 
breathing siphon on its back at the tail end. The larva is lighter 
than water; when feeding or at rest, it floats just below the surface 
and parallel to it; when disturbed it wriggles vigorously from side to 
side, the motion sometimes carrying it downward but more frequently 
sideways. When at the surface, the end of the breathing siphon 
pierces the “‘surface film,’’ opens up, and exposes the ends of the 
trachee, the tubes which convey air to all parts of the creature’s body. 
In order to feed on the microscopic plants and other organic material 
floating at the surface, the larva twists its neck until its mouth is on a 
line with its back. While there are other, more technical characters, 
it is sufficient to say that a mosquito larva which has a short, stubby 
breathing siphon, floats parallel with the surface of the water, and 
twists its head to feed is an Anopheles. The Culex larva floats at an 
angle with the surface as shown in Fig. 16, and has a relatively long 
breathing siphon. 
As a young insect feeds, its flesh increases but its skin does not 
stretch sufficiently to accommodate the enlarging body. Therefore, 
the old skin is cast from time to time and a new, larger skin is 
formed. Finally there comes a time, as in the case of such insects 
as moths and beetles, which like the Diptera have a “‘complete 
metamorphosis,’ when there emerges from a larval skin something 
which is neither larva nor. adult, and which is called the pupa. The 
pupa of moths is, for the most part, immobile and frequently enclosed 
in a protective case, the “cocoon,” which is spun for it by the larva. 
The pupa of mosquitoes is active, but not so active as a larva, and it 
does not feed. It also differs from the larva in being hunched up 
instead of slender and in having a pair of breathing siphons on its 
thorax (the part of the body just back of the head) instead of a single 
siphon on the tail. The pupa of Anopheles closely resembles that of 
Culex, but the abdomen is more sharply curved and the breathing 
siphons are more dilated at the top and relatively shorter than in 
Culex. The adult mosquito finally emerges from a:split in the back 
of the cast pupal skin, which forms a miniature boat upon which the 
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