AIR-PIPES OF INSECTS. 403 



along the abdomen, and situated at the side of the 

 wings, and is received by a large tube on each 

 side of the body, running its whole length, or 

 nearly so, as we before mentioned. This tube, and 

 those which it gives off as branches, are called 

 tracked) or air-pipes. The tracheae are formed 

 in the most wonderful manner, so as to keep 

 them always open, that the air can readily pass 

 through them. Perhaps some of our readers 

 have seen the contrivance adopted by sailors in 

 order to blow air down into the hold and cabins 

 of the ship ; for those who have not, we may 

 take the liberty of mentioning, that it is a large 

 tube made of canvass, open at the side near the 

 top, so as to catch the wind, while the bottom of 

 it opens into the cabin. Now, the sailors always 

 place the mouth of this tube towards the wind, 

 which is forced down the tube into the cabin 

 either by its own speed, or by that of the vessel, 

 in the case of a steamer, and so fills the cabin 

 below continually with fresh air. But, it will be 

 asked, how do they contrive so to keep the sides 

 of the bag from flapping together as to prevent 

 them from closing ? By imitating a contrivance 

 which exists in the trachea or air-tube of the 



