INSECTS: THEIR BREATHING ORGANS 113 



vessels still. 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 de- 

 prive 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 

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

 suffocated; for phosphoric and sulphuric acids intro- 

 duced into the breathing tubes quickly destroy life. I 

 presently take it out, and putting it into a dissecting- 

 trough under a lens, cut up the abdomen with a pair of 

 fine-pointed scissors. Then I pin open the divided abdo- 

 men to the bottom of the trough, which is coated with 

 wax for the purpose; and, looking at it with the lens 

 but you shall look for yourself. 



"Well, you see little else but the polished brown walls 

 of the body and a number of fine white threads. It is 

 those threads that we want. With a small camel's hair 

 pencil I move them to and fro in the water, and soon per- 

 ceive that they are like little trees with comparatively 

 thick trunks, sending off many branches, and gradually 

 becoming excessively slender. Here and there short thick 

 branches break out on two opposite sides, and on each side 

 are connected with the wall of the abdomen. Here then 

 with the fine scissors I snip them across, and lift up a 

 portion with the hair pencil into a drop of water which I 

 have already put into the live- box. The cover now flat- 

 tens the drop, spreads the white threads and the object 

 is ready for our eye. 



