How insects move 



Fig. 56. Head and thorax of a rat-flea from the Argentine, which has an 

 elaborate set of combs 



The wing-tip generally follows a figure-S, or crossed-loop pattern, 

 going downwards and forwards, upwards and back. Like an oarsman, 

 the insect squares its blade on the downward, or power stroke, and 

 feathers it for the recovery. All the elaborate control is achieved by 

 varying the angle of the blade, and its speed of movement, at different 

 points of the path, and by changing the plane of the stroke on one or 

 both sides. The most expert fliers, such as the bees and the hoverflies, 

 have complete control in the air, and can hover motionless, rise or fall, 

 or dart forwards, or backwards, or to either side, simply by altering the 

 stroke-plane of the wings. 



How is the insect able to make such delicate adjustments with such 

 speed and precision? In the base of the wing there are nerves, and a 

 number of sensillae, rather hke those we have mentioned before in con- 

 nection with hearing. These tell the insect what the wing is doing, just 

 as we ourselves can move our hand behind our back, without being able 

 to see it. In addition there are certain reflexes, or automatic actions which 

 concern flight. If the tarsi of the legs cease to press against a sohd 

 surface most insects will begin to fly. Once the insea has begun to move 

 through the air it seems to be aware of the flow of air over its antennae, 



83 



