1. Behaviour termed ‘stilting’ is described for the scorpion, Opisthophthalmus latimanus. In this pattern the legs are straightened, lifting the body clear of the substratum.
2. Evidence is submitted that it is not concerned with allowing greater respiratory exchange.
3. Stilling is generally elicited in response to a rise in environmental temperature above 18° C. and is invariably found at temperatures above 28° C.
4. A comparison using scorpions held in the stilted and normal resting stance, shows that, when the environmental temperature rises sharply, the body temperature of the resting animal rises rapidly, while that of the stilting animal is almost unchanged. The mechanism of this effect is shown to be due largely to the increased circulation of air around the animal which is permitted by the stilting.
5. From observations of behaviour in both the laboratory and the field, it appears probable that the stilting pattern is shown by O. latimanus during the hot hours of the day when the scorpion waits in the entrance of its burrow to catch prey.
6. Laboratory observations indicate that when the temperature becomes so high that stilting has no longer any protective value, a photopositive reaction, which would keep the scorpion at the entrance of its burrow, changes to a photonegative one and the animal can retreat into the cool depths of its burrow.