160 THE LORE OF THE HONEY-BEE 
hooks along its top edge, while the lower edge of 
the upper wing is flanged or folded back. In 
flight the hooks on one wing engage with the 
flange on the other, and thus the wings on each 
side are automatically locked together, forming one 
continuous air-resisting surface. This combined 
wing is very flexible throughout, except at its 
upper edge, where it is stiffened by the main rib. 
In action, therefore,—the force being applied 
practically to the edge alone, which resists the air 
while the rest of the wing bends to it—the result 
is that the whole wing becomes an oscillating, 
inclined plane, whose inclination, forward on the 
down-stroke, is still forward on the up-stroke, 
because the plane-inclination reverses itself auto- 
matically. 
From this it will be understood how the flexible 
wings of the bee are used in straightforward 
flight; but, seeing that the wings themselves are 
incapable of independent or irregular action, it is 
not yet clear how the bee contrives to steer herself, 
rising or descending, or turning sideways, just as 
the mood seizes her. It is here that the reason 
for the peculiar construction of her body becomes 
plain. The fine link which unites her abdomen 
to her thorax is really an universal joint, actuated 
by a series of powerful cross-muscles, and the bee 
steers herself through the air by using the weight 
of the lower half of her body as a counterpoise. 
By swinging her heavy abdomen forward or back- 
