MUSCLES AND MOVEMENTS 111 



halteres. These are modified hind-wings richly supplied with cam- 

 paniform organs (p. 118) which can detect strains set up in the cuticle. 

 Such strains can be set up in the vibrating halteres by the inertia 

 forces exerted when the flying insect deviates from its normal course. 

 The halteres act as gyroscopic sense organs adapted to perceive de- 

 viations from their plane of vibration. In the dragon-fly Anax, also, 

 the flying insect maintains its equilibrium by means of at least three 

 sensory reactions: a reaction to the general visual pattern, a reaction 

 which ensures that the main source of illumination remains dorsal, 

 and a response to tactile hairs stimulated by the inertia of the head. 

 Furnished with such sense organs good insect fliers can steer accu- 

 rately; they can hover, go sideways or backwards, or rotate round 

 the head or the tip of the abdomen, 



BIBLIOGRAPHY 



boettiger, e. g. Ann. Rev. Entom., 5, (1960), 53-68 (flight muscles and 



flight mechanism: review) 

 hughes, g. m. Physiology of Insecta II (Morris Rockstein, Ed.), 1965, 227- 



256 (locomotion of insects on land) 

 pringle, J. w. s. Insect Flight, Cambridge University Press, Physiology of 



Insecta II (Morris Rockstein, Ed.), 1965, 283-329 (insect flight) 

 sacktor, b. Physiology of Insecta II (Morris Rockstein, Ed.) 1965, 483- 



580 (biochemistry of muscular contraction) 

 wigglesworth, v. b. The Principles of Insect Physiology, 6th Edn., 



Methuen, London, 1965, 129-155 (muscles and locomotion in 



insects) 



