The Two-winged Flies 
3°7 
pupae (Figs. 413 and 415) with thick, broad head end (the thick part includes 
thorax and head) and slender, curving abdomen, bearing two conspicuous 
swimming-flaps at the tip. The pupa rests at the surface of the water with 
its two short horn-like respiratory tubes, which rise from the dorsum of the 
thorax, extending through the surface film to the air above. When dis¬ 
turbed it swims swiftly down into the water by quick bendings or flappings 
of the abdomen with its terminal flaps. The pupal stage lasts from two to 
five days, with comparatively little variation beyond these extremes. 
The adults issue through a longitudinal rent in the back of the pupal 
cuticle, and while drying their wings, legs, and body vestiture rest on the 
surface of the water, often partly supported by the floating discarded skin. 
The two wings are long and narrow, the legs long and slender, the thorax 
humped with the small head hanging down in front and the slender sub- 
cylindrical abdomen depending behind. The body is clothed with scales, as 
are the veins of the wings, and on the scales, which are of different shapes 
and sizes on different parts of the body, and vary in different species, depend 
the colors and pattern, often striking and beautiful, just as all the color pat¬ 
terns of the butterflies and moths are produced by a covering over body and 
wings of similar scales. The males of all mosquitoes differ from the females 
in having the slender, many-segmented antennae provided with many long 
fine hairs arranged in whorls and combining to give the antennae a bushy or 
feathery appearance. These hairs, as has been proved by experiment and 
histologic study, are a part of an elaborate auditory apparatus, their special 
function being to be set into vibration when impinged on by sound-waves of 
certain rates of vibration, and to transmit this vibration to a complex nervous 
organ in the second antennal segment (Figs. 56 and 57). The males, while 
having a long, slender, sucking-proboscis, do not possess the piercing sty¬ 
lets characteristic of the female, and hence are not blood-suckers, but prob¬ 
ably feed, if at all, on the nectar of plants or on other exposed liquids. The 
females suck blood when they can get it, but in lieu of this animal fluid 
feed on the sap of plants. In experimental work in the laboratory cut 
pieces of banana are provided the imprisoned adult mosquitoes. 
At this writing about fifty species of Culex, one species of Stegomyia, and 
four species of Anopheles have been found in this country. These three 
genera may be distinguished by the following key: 
Palpi (the mouth-feelers projecting by the side of the proboscis) long in both male and 
female, about as long as the proboscis. Anopheles. 
Palpi as long as proboscis in male, but only one-third as long in female. 
Scales on the head narrow and curved. Culex. 
Scales on the head flat and broad. Stegomyia. 
Our particular interest in being able to distinguish these genera lies, as 
already said, in the special relation which their members bear to certain 
