128 



RELATION OF WING SURFACE TO WEIGHT. 



terflv has 1 1.('>()0. Careful (»l)servatioii shows, however, that in the main 

 the variation of tliis ratio depends on the size of the animal, or, stated in 

 g-eneral terms, the winijs are rehitively hirger the smaller and lighter 

 the animal to which thev belong. It is shown also that the variations 

 from the general rule depend on the fact that the mode of flight is dif- 

 ferent in different animals. Some flying creatures overcome weight by 

 the rapid movement of their wings; others, especially at the beginning 

 of a stroke, take advantage of the internal atmospheric currents, and 

 use the enormous resistance of the air for their purpose. The first 

 class, to which the sparrow and the honeybee belong, may be desig- 

 nated as flapping flyers, and the last class, of which the albatross and 

 the sea eagle are examples, as sailing flyers. These extreme types of 

 the so-called flapping and sailing flyers are connected by an unbroken 

 chain of flying creatures, not all of which are so exclusively either 

 flappers or sailers as the birds just named. 



As might be expected, the flapping flyers have comparatively small 

 wings, which move swiftly by the aid of powerful muscles, while the 

 wings of the sailers are moved by weaker muscles and more slowly. 

 If Ave take these two classes into consideration separately, as in the 

 following tables, it is clearly shown that the wing surface increases 

 with decreasing w^eight of body. 



Flappers. 



Animal. 



Weight. 



Wing sur- 

 face to 1 

 gram 

 weight. 



Bu.stard ... 

 Pheasant . . 

 Partridge.. 

 Sparrow . . . 

 Bumblebee 

 Honeybee . 

 House fly.- 

 Gnat 



Grams. 

 9,600 

 1,000 

 320 

 28 

 .44 

 .074 

 .01 

 .003 



Mm-i 



62 



88 



ia5 



200 

 234 



528 

 1,800 

 10, (XX) 



Sailers. 



Animal. 



Albatross 



Sea eagle 



Stork 



Silver gull... 



Sparrow hawk . . . 



Laughing gull 



Virgin dragon fly 

 Lemon butterfly. 



