Underwater locomotion in the desert locust: behavioural choice when confronted with an acquatic barrier.

Laboratory studies have shown that adult desert locusts (Schistocerca gregaria) have a swim motor programme, and early field reports describe swimming by bands of hoppers if their route of march is obstructed by a channel of water. However, it is not known whether unconstrained adult locusts will enter water 'voluntarily'. We found in the laboratory that not only will locusts readily enter water, but that they frequently submerge themselves completely under the water, and cross a water barrier by walking along the bottom. They can stay submerged for up to approximately 9 min, but there is no evidence for significant gas exchange with the water. So far as we are aware the demonstration of this capability for underwater locomotion is a novel finding in this well-studied insect.