INSECTS : THEIR BREATHING ORGANS. 93 



CHAPTER VI. 



INSECTS : THEIR BREATHING ORGANS. 



In order to understand the passage last quoted from 

 Burmeister, you ought to know something of the manner 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 oxygen 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 such in their earlier stages. Even in 

 exceptional cases, viz., those larvaa or pupae which are 

 provided with what represent gills, and appear to be 

 dependent on the water for their respiration, the excep- 

 tion is rather apparent than real, for the function is still 

 performed in air-vessels. Now these air-vessels shall 

 afford us some interesting microscopical observations. 



This brown fly, which is buzzing and hovering on in- 

 visible wings over the flowers in the garden, you perhaps 

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

 caught it, and you may ascertain the fact for yourself; 

 it belongs to the genus Syrphus. Having caught it, I 

 deprive it of life by means of the very organs I am going 

 to examine, for I turn a tumbler over it and insert under 

 the ed^e a lighted lucifer-match. In a few seconds it is 

 dead — suffocated; for phosphoric and sulphuric acids 



