Laboratory observations on factors affecting the movements of hoppers of the desert locust

Laboratory Observations on Locust Responses to Wind‐borne Grass Odour

“…The experiments leave many unanswered questions including the nature of the sensory cues in anemotaxis, but they leave little grounds for the suggestion of Haskell et al (1962) that the upwind movement of locust hoppers toward a source of grass odour is osmotropotaxis mediated by the antennae. Grass odour can induce such movement in hoppers with crossed-over antennae, and with one or both antennae removed; and anemotactic upwind orientation can occur without any grass odour in hoppers that have been handled and tumbled together.…”

“…The arguments in support of the alternative osmotropotactic hypothesis of Haskell et al (1962) were as follows. When one antenna was covered with vaseline or removed the hoppers responded to grass odour in wind by making the circus movements typical of tropotaxis, and when both antennae were vaselined they responded by moving downwind like hoppers with untreated antennae in wind without grass odour.…”

“…In preliminary experiments in steep grass odour gradients in still air, we have observed turning responses toward the odour source by intact hoppers, but only when the source and the "sink" (activated charcoal) were about l0 cm apart. Lastly, the negative results of eliminating particular mechanoreceptor inputs cannot be conclusive evidence against anemotaxis, whether mediated by mechano-or other receptors, especially when there is already evidence that temperature receptors detecting differential cooling of the body may be involved in the downwind movement of basking hoppers (Haskell et al, 1962).…”

“…Thus there was again a build-up of locomotor excitability as the series of tests proceeded. The hoppers did not start from a constant low level of locomotory activity, basking quietly on the floor, in the successive tests with increasing starvation as they did in the experiments of Haskell et al (1962) and of Moorhouse (1969) mentioned in the Introduction. Hence, as can be seen in Fig.…”

“…The wind tunnel used was the original one described by Haskell et al (1962), with a working section 120 cm long, 71 cm wide, and 13 cm high, but without the electric fences at the two ends. The locusts were thus able to climb the muslin covers of the end honeycombs and commonly did so on arrival at either end, and this set a limit to the time available for observations of behaviour on the sand floor of the tunnel after any given stimulus onset.…”