106 EVENINGS AT THE MICEOSCOPB. 



CHAPTEE YI. 



INSECTS : THEIE BEEATHING OKGANS. 



In order to understand tlie passage last quoted from 

 Burmeister, you ought to know something of the man- 

 ner in which breathing is performed among insects. 

 Essentially, breathing is the same function, wherever 

 it occurs ; and it does occur, doubtless, in all animals 

 under some form or other. It is the absorption of oxy- 

 gen from without to the fluids within, to repair the 

 waste constantly produced by vital energy. But it 

 may be obtained from different sources, and imbibed in 

 various modes. 



All insects in the perfect state are air-breathers ; 

 that is, they procure their oxygen from the air as we 

 do ; and most of them are so in their earlier stages. 

 Even in exceptional cases, viz., such larvse or pupee as 

 are provided with what represent gills, and appear to 

 be dependent on the water for their respiration, the 

 exception is rather apparent than real, for the function 

 is performed in air-vessels still. Now these air-vessels 

 shall afford us some interesting microscopical obser- 

 vations. 



This brown fly, which is buzzing and hovering on 

 invisible wings over the flowers in the garden, you 

 perhaps take for a bee. No ; it has but two wings ; 



