MECHANORECEPTION 65 



that proprioceptive information about the position of the antennae 

 relative to the head supplements information from Johnston's organ 

 for steering flight velocity. 



When the funiculi of the fly's antennae are rotated in their sockets 

 and fixed in the position which they would normally assume if wind 

 were blowing on them the flies fly much more slowly than controls 

 (Burkhardt and Schneider, 1957). In aphids flight is impaired when the 

 flagella of the antennae are removed; however, when artificial flagella 

 are supplied as replacements control is regained (Johnson, 1956). 



Change in velocity of flight can be eff'ected in a number of ways. The 

 experiments of Hollick (1940) with Mucina showed that these flies 

 shift the path travelled by the wing tip cranially if they are subjected to 

 a current of air from in front and if they are in possession of their 

 antennae. In the absence of antennae, there is no shift. Wing-beat 

 amplitude is also altered as a result of information received through 

 the Johnston's organ. Bees reduce the wing-beat amplitude in the face 

 of air currents, but if they lack antennae the reduction is less marked 

 (Heran, 1959). In the case o{ Aedes there is a greater wing-beat ampli- 

 tude in air currents when antennae are lacking than in still air when 

 antennae are intact (Bassler, 1957, 1958). 



Burkhardt and Schneider (1957) had pointed out that the antennae 

 of Calliphora also respond electrophysiologically to sound in the range 

 1 50-250 c/s, the same range as the wing-beat frequency. They proposed 

 that this response might possibly be employed to register the acceler- 

 ation due to each wing-beat, since the funiculi of the antennae vibrate 

 at this frequency as a result of the discontinuous air stream arising with 

 each wing thrust. Support for the hypothesis is derived from the obser- 

 vation that the resonance frequency of the bee's antennal flagellum 

 also agrees well with the wing-beat frequency, and the Johnston's 

 organ is most sensitive to vibrations of 200-350 c/s (Heran, 1959). 

 No tonic component similar to that detected in Calliphora can be seen 

 in electrical activity in the bee's antenna. Furthermore, if vibrations 

 too fast for the flagellum to follow are forced upon the antenna it is 

 bent outwards but no longer vibrates, and the bees do not respond to 

 the change in position (Heran, 1959). 



Information from the Johnston's organ is also used to correct yaw. 

 In turning about the vertical axis the angle of attack of the antenna 

 on the outside of the turn becomes larger. Since intensified current on 

 an antenna reduces wing-beat on the same side, a passive rotation 

 produces an active torque in the opposite direction by which the 

 straight flight course is stabilized (Heran, 1959). 



