The T\vo-v\ inged Flies 307 



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-tlaps at the tip. The pupa rests at tlie surface of the water with 

 its two short horn-Hke respiratory tubes, which rise from the dorsum of the 

 thora.x, 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 da\'s, with comparatively little variation beyond these extremes. 



The adults i.ssue through a longitudinal rent in the back of the pupal 

 cuticle, and while drying their wings, legs, and body vestiture re.st 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 ditTerent parts of the body, and vary in different species, depend 

 the colors and pattern, often striking and beautiful, ju.st 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 antenna; 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 .\nopheles 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 



