EXTERNAL ANATOMY OF INSECTS. 67 



and to contain muscle to guide and govern them, a body must 

 be added. Each part of the body will be of best size, and best 

 form, for the functions it has to perform. We have seen that 

 insects, in the larva state, have a very uniform allowance of 

 muscle to each segment. In the imago, the charge of support- 

 ing the whole body in the air is entrusted sometimes to a single 

 segment ; and, in order to supply sufficient strength for the pur- 

 pose, nature robs the neighbouring segments of their muscle, 

 and gives it the one which needs it. In the head, the mouth, 

 feelers and eyes operate, in the same manner, one on another. 

 Observe the dragon fly, the emperor of his tribe : q his wings 

 rustle as he hovers stationary and hawk-like in the air ; his 

 appetite is insatiable ; his food, the active occupants of his 

 own element, — it is given to him in charge to set bounds to 

 the increase of the insect race ; he beholds his prey afar off; 

 he darts on it with the rapidity of a lightning-flash. To 

 devour it, ere life is departed, is the work of an instant. He 

 sails round and round ; he soars up and up. When the sky 

 is serene he seeks his prey, like the swallows, almost beyond 

 the reach of human sight. What organs does such an animal 

 require ? Are they not these ; eyes, mouth, and wings ? How 

 has Nature provided for his wants ? Regard his head : below, 

 it is all mouth ; above, it is one continuous eye. Contemplate 

 his wings : their character is strength and lightness, power 

 and activity. His body is slender and graceful ; like a rudder, 

 it serves as an instrument wherewith to shape his course. 

 Porrected feelers, whether cranial, labial, or maxillary, would 

 be comparatively useless to an animal whose dependence for 

 support is on the keenness of its vision and the velocity of its 

 flight. We find them but little prominent ; his every organ 

 of the required size. The same law obtains as certainly 

 and unvaryingly in form. There is truly a best size and a 

 best form, and nature always provides it. 



The fixed organs of the head, manifesting but slight variations, 

 require no further comment. The antennce or cranial feelers, and 

 the mouth, are the only moveable organs. The antennce are too 

 well known to dilate on. The mouth must be considered more at 

 large. The union of the head with the jirothorax is by an articu- 

 lation much more free than that between either of the following 



i Genus Anax of Leach. 



