. The animans and man; an elementary textbook of zoology and human physiology. ng stage of any insect which differs markedlyfrom the fully developed or mature one is called the larvalstage. The larvae swim actively about. By what means do theyswim? If they cease swimming do they sink deeper in thewater or rise to the surface ? Is the body of the larva denser MOSQUITOES AND CATERPILLARS or less dense than the water ? that is, is it heavier or lighterthan water? Note that some of them hang quietly fromthe surface, and that each one comes occasionally to thesurface and reststhere for a while tobr
. The animans and man; an elementary textbook of zoology and human physiology. ng stage of any insect which differs markedlyfrom the fully developed or mature one is called the larvalstage. The larvae swim actively about. By what means do theyswim? If they cease swimming do they sink deeper in thewater or rise to the surface ? Is the body of the larva denser MOSQUITOES AND CATERPILLARS or less dense than the water ? that is, is it heavier or lighterthan water? Note that some of them hang quietly fromthe surface, and that each one comes occasionally to thesurface and reststhere for a while tobreathe. Every ani-mal has to breathe;that is, to take upoxygen from the airand to give off fromits body carbon di-oxide (CO,). Thereis always some airmixed with or dis-solved in water,and most aquaticanimals—fishes forex a m p 1 e—havespecial structurescalled gills whichenable them to takeup this dissolvedoxygen, and thus tobreathe under wa-ter. But the gillsof most mosquitolarvae are too un-developed, andtherefore they haveto come occasional-ly to the surface A mosquito, Culex sp.; showing eggs(on surface of the water), larvae (long andslender, in the water), pupa (large-headed atsurface), and adult (in the air). (About threetimes natural size; from living specimens.) Examine with a hand lens one of the larvae in a watch-glass of water. Distinguish the head end of the body;note the eyes (two small black spots), the feelers, or antennas, 88 THE ANIMALS AND MAN and a pair of tufts or brushes of hair on the head whichvibrate rapidly and constantly. These brushes by theirvibration create currents in the water setting toward themouth, which lies between them, and thus bring food to food consists of any tiny animalcules and microscopicbits of organic matter in the water. Are there any legs orwings? Examine the posterior end of the body and noteits division into two parts—one the end of the hind bodyor abdomen, the other a breathing-tube projecting fromthe ne
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