INSECTS : THE1B BEEATHTNG OBGANS. 93 



CHAPTER YI. 



INSECTS I THEIB BREATHING OBGANS. 



In order to understand the passage last quoted from Bur- 

 meister, 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 larvae or pupa? which are pro- 

 vided with what represent gills, and appear to be de- 

 pendent on the water for their respiration, the exception is 

 rather apparent than real, for the function is still per- 

 formed in air-vessels. Now these air-vessels shall afford 

 us some interesting microscopical observations. 



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 ; 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 Hfe by means of the very organs I am going 

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

 the edge a lighted lucifer-match. In a few seconds it is 

 dead — suffocated ; for phosphoric and sulphurie acids in- 



