WINGS AND FLIGHT. 143 



lying between a and b, Fig. 28. But should the 

 bee desire to reverse her movement, decreasing the 

 energy of the larger wing, and increasing that of 

 the* smaller, instantly accomplishes her purpose, with- 

 out any stoppage of flapping, because the then 

 stronger beat of the small wing, and the restricted 

 beat of the larger, immediately reverses the set of 

 their united plane. By examining DSB, Fig. 29, 

 we shall see the truth of this. Here the wider move- 

 ment of pw (the posterior wing) makes it the leader, 

 producing the alteration that would have arisen from 

 transferring the stick to the opposite edge of the 

 paper (Fig. 28), and the air is, in consequence, 

 beaten in the opposite direction (c'), so that the 

 bee is carried backwards, abdomen first. The up 

 stroke, as before, producing the same current as 

 the down, another Figure is. not needed to repre- 

 sent it. The case is that of a screw steamer 

 which, without stopping her engines, reverses her 

 course by changing the direction of the pitch of the 

 arms of her propeller. This, however, is my theory, 

 as distinct from that of Gelieu, which is immensely 

 more complex, and would require a nervous control, 

 which seems to me utterly incredible. 



The question of ascending or descending now 

 suggests itself. This has been fully investigated by 

 Marey,* by means of adjustable models, of which 

 our space will not permit a description. Observations 

 on bees themselves have led me to the following 

 conclusions : The wings, during flight, are the points of 



* "A Treatise on Terrestrial and Aerial Locomotion" (International 

 Science Series). 



