196 FIELD ZOOLOGY. 



When the air in the tracheal system is exhausted, the 

 wriggler backs up to the surface of the water, holds on by 

 the tension of the water molecules, opens up these tiny 

 flaps, and breathes its tracheal system full of air again. 



The larval stage lasts from one to four weeks or even 

 longer, according to government investigations, depending 

 upon the species, the season, and the varying conditions 

 of food supply, temperature, water, and light. After 

 the third moulting of the larvae they appear as pupas, 

 each having a thick head end, which includes the slenderer, 

 curving abdomen. Now the respiratory tube ends 

 exteriorly by two tubes which arise from the upper side 

 of the thorax. The pupal stage lasts from one to five 

 days for the different species. 



If you have been watching some standing water 

 with some of these mosquito wrigglers in it, in the course 

 of time, many of these curved pupae may be observed. 

 They hang at the surface of the water and do not go below 

 unless the water is disturbed, or they are frightened by 

 some other means. Then they move downward with a 

 curious jerking motion made by repeatedly flapping the 

 slender abdomen against the big head end of the body. 

 These pupae are an exception to the usual pupal con- 

 dition; they are non-feeding, as pupaa usually are, but 

 they are very active. Most pupae carry on their marvelous 

 changes on the way to adulthood in some case or cocoon, 

 hidden from our eyes and to all appearance motionless. 

 But the mosquito "tumbler" lives -alongside his younger 

 brothers and sisters, in the same medium, breathing as 

 they do, and gradually developing wings and long legs, 

 antennae and new mouth-parts, all the while being jostled 

 about by numberless other creatures in their tiny ocean. 



Soon after the first one of these "tumblers" appears, 



