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that it is one of the minute, non-filterable organisms called spirochetes. The virus will hot develop m the mosquitoes at a temperature below 68 ° F., and ,tëdes

aegypti will not breed /" in latitudes much be- "'\), ,,// yond the possible range of yellow lever. -,,/ Yellow fever, there- fore, is a disease ordi- narily confined to tbe ?, tropics and warmer j/Ù.-\ parts of the te tope r- ate zones. Season- . al outbreaks of it that have occurred in // \ northern cities have been caused probably by local infestations // \ of infected mosqui- / / ] toes brought in on Fie.. 18o. The female malaria mosquito, ships from some .4nopheles punctipennis SOU thern port. The malaria mos-

quitoes belong to the genus .tnopheles, a genus repre- sented by species in most temperate and tropical regions of the world, which are prevalent wherever malaria oc- curs. Our most common malaria species is «qnopheles punctipennis (Fig. 8o), characterized by a pair of dull white spots on the edges of the wings. The .tnopheles females lay their eggs singly on the surface of the water, where they float, each buoved up by an air jacket about its middle. The larvae of Anopheles (Fig. 78 B) differ conspicu- ously from those of Culex and Aëdes both in structure and habits. Instead of a respiratory tube projecting from nea the end of the body, as in Culex (Figs. 174 E 75), there is a concave disc (Fig. 78 B,f) on the back of the next to

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MOSQUITOES