. Preventive medicine and hygiene. Fig. 23.—Head of Stegomyia Calopus (male). 340 INSECT-BOENE DISEASES \ rapidly to the bottom, where, indeed, it may very commonly be observedto feed. The duration of the larval sta^e is never less than 6 to 7. Fig. 24.—Eggs of Stegomyia Calopus. days, and depends upon the food supply and temperature. Under certainunfavorable conditions it may be prolonged for weeks. Freezing for shortperiods does not appear to injure it. Pupa.—The larva changes into the pupa. The pupa is not provided

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Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene