Hkitisii Hloodsickkrs 



241 



as a locomotive device everybody kno\v> who lias 

 once tried chivvyiiiij a few healthy mosquito larv;e 

 round the brimming sea of his bedroom basin. 



The breathing - tube deserves a little longer 

 notice. By its means air is conveyed direct into 

 the internal air-channels of the insect, which do 

 not form lungs, 

 but ramify like 

 arteries all over 

 the body. We 

 carry our blood 

 to the lungs to 

 be aerated ; the 

 insects carry the 

 oxygen to the 

 blood. To take in 

 air, the larva fre- 

 quently rises to 

 near the surface, 

 as vou see him 

 doing in Xo. 4 ; 

 then he stands on 

 his head, cocks up 

 his tail, and pushes 

 t)ut his air-tube. 



Indeed, when at rest this is his usual attitude. 

 Xo. 5, which, of course, is very hignly magnified, 

 shows his tail in the act of taking in a good gulp 

 ot oxygen. The little valves, or doors, which 

 cover the air-tube are here opened radially, and 

 the larva is breathing. To the right you see the 

 position of the tube after he has taken in a long 



g 



Ml. 5. IIIK lAKVAS HRKA I inMi-l UKl 

 l.I.OhKH AM> (il'KN. 



