. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 446 MOSQUITOES water and even in brackish water, provided food material, in the form of dead organic matter and the accompanying bacteria, is present. Atkin and Bacot have recently shown that the food consists almost, if not quite, exclusively of bacteria, and that when the larvae are present in large numbers they exert a considera- ble influence in the purification of water. Often the larvae are over- looked, since they immediately wriggle to the bottom of their dwelling place when approached, and hug
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 446 MOSQUITOES water and even in brackish water, provided food material, in the form of dead organic matter and the accompanying bacteria, is present. Atkin and Bacot have recently shown that the food consists almost, if not quite, exclusively of bacteria, and that when the larvae are present in large numbers they exert a considera- ble influence in the purification of water. Often the larvae are over- looked, since they immediately wriggle to the bottom of their dwelling place when approached, and hug the bottom so closely that even if a barrel containing thousands of them is turned over on its side, about 80 per cent will stay in the little remaining water. The larvse feed exclusively on the bottom and can often be seen nibbHng away at a dead insect or bit of decaying vegetation. With plenty of food and at favorable temperatures the larval existence may be completed in four days, according to Bacot, though it usually requires a longer time than this, and may be drawn out to two months or more. The larvae are not resistant to dry- ing, and die in a few hours in a Fig. 204. Larva of yellow fever dry place, though capable of liv- mosquito, Aedes caiopus. X 10. [^„ nearly two wccks ou moist (After Howard, Dyar and Knab.) i ground. The pupae (Fig. 205) transform, under normal conditions, in a day and a half or two days. The entire cycle from egg to adult seldom takes place in less than nine or ten days, and probably 12 or 15 days is more usual under ordinary conditions. As has been shown above, the period of development may be drawn out over several months by unfavorable conditions. The adult mos- quitoes may Uve for a considerable time, and apparently are able to transmit yellow fever any time from 12 days after in- fection to the end of their lives. Male mosquitoes ordinarily. Please note that these images are extracted from scanned page images that may have been digitally e
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