1. Injury to one side of the face, whether on the frons or an antennal patch, affects the orientation of adult locusts to a lamp. For the first 5 days after injury most of them turn the injured side towards the lamp. This tendency is lost or reversed after the fifth day. The change is most evident with a lamp of relatively high power (100 W.); with weaker lamps (60 or 40 W.) the differences are not statistically significant after five days.
2. This phenomenon explains the finding of previous authors that the injured side is usually turned away from a lamp. When the results of numerous tests are added together, those obtained more than 5 days after injury can swamp the earlier ones.
3. Suggested interpretations include the possibility that injury makes the damaged part ‘numb’ until type II neurones are formed in the healed area.