OF INSECTS. 305 



is necessarily forced through the only openings which 

 present themselves. The **iore rapid the flight, tse 

 greater must be the muscular action, and, conse- 

 quently, the expulsion of the air more violent; 

 conditions which perfectly accord with the variom 

 degrees of intensity observed in the sounds emitted 

 in different states of movement. When a portion 

 of the wing is cut off, the rapidity of flight is neces- 

 sarily diminished, and the muscles contract but 

 feebly, in consequence of the lever which moved 

 them being shortened. If the lever be completely 

 taken away, which cannot be done without the 

 laceration of some of the muscles, the contracting 

 power cannot be exercised with sufficient force to 

 eject the air, or, in other words, produce sound. 

 In accordance with this view, the sound is found 

 to be immediately stopped, if the apertures of the 

 spiracles be filled up with gum or any other ad- 

 hesive substance, and cannot of course be produced 

 in whatever state the wings may be. 



The abdomen in hymenopterous insects is often 

 very small, and in some extensive tribes it is at- 

 tached to the thorax by a very slender segment 

 forming a kind of foot-stalk. The most remarkable 

 appendage connected with it is the ovipositor, which, 

 in most tribes, is very much developed. This in- 

 strument assumes a great variety of forms in diffe- 

 rent families to adapt it to their diversified economy ; 

 and, in all, exhibits a beautiful example of mecha- 

 nical contrivance. 



The members of this interesting order usually 



