Insect Study 



401 



under, revolving their brushes 

 briskly; but they never remain 

 very long below the surface, as it is 

 necessary for them to take in fresh 

 air often. 



The pupa has the head and 

 thoracic segments much enlarged, 

 making it all "head and shoulders" 

 with a quite insignificant 

 body attached. Upon the 

 thorax are two breathing 

 tubes, which look like two 

 ears, and therefore when 

 the pupa rests at the sur- 

 face of the water, it remains 

 head up so that these tubes — - — " 

 may take in the air; at the 

 end of the body are two 

 swimming organs which are little, 

 leaf-Hke projections. At this stage 

 the insect is getting ready to live 

 its Hfe in the air, and for this reason 

 probably, the pupa rests for long 

 periods at the surface of the 

 water and does not swim about 

 much, unless disturbed. How- 

 ever, it is a very strange habit 

 for a pupa to move about at all. 

 In the case of other flies, butterflies, 

 and moths, the pupa stage is quiet. 



When fully mature, the pupa 

 rises to the surface of the water, 

 the skeleton skin breaks open 

 down its back and the mosquito 

 carefully works itself out, until 

 its wings are free and dry, mean- 

 while resting upon the floating 

 pupa skin. This is indeed a frail 

 bark, and if the slightest breeze 

 ruffles the water, the insect is 

 likely to drown before its wings 

 are hard enough for flight. 



The reason that kerosene oil, 

 put upon the surface of the water 

 where mosquitoes breed, kills the 

 insects is because both the larvge 

 and pupae of mosquitoes are 

 obhged to rise to the surface, and push their l:)reathing tubes through 

 the surface film so that they will open to the air; a coating of oil on the 

 water prevents this, and they are suflocated. Also when the mosquito 

 emerges from the pupa skin, if it is even touched by the oil, it is unable 

 to fly and soon dies. 



A wriggler or larva of 

 mosquito (culex) greatly 



enlarged. 

 Drawn by Evelyn Mitchell. 



