The behaviour of individual coccinellid larvae on plants

Summary The behaviour of coccinellid larvae on plants was studied. They moved on bean leaves, as they did on a flat piece of paper, with frequent changes in direction, but the edges and prominent veins of leaves often determined the pattern of their tracks. The chance touching of leaves of adjacent plants influenced their direction of movement and, when aphid colonies on bean plants were few, larvae might by chance be led far away from them. Coccinellid larvae wasted time and energy in repeatedly visiting parts of plants which they had already visited. Larvae which encountered aphid coloniestended to stay near them, because after feeding they made small turning movements from side to side, which increased the chance of meeting another aphid of a colony. This behaviour was different from the behaviour before feeding. Fleschner's (1950) conclusion that larvae are unable to perceive the prey from a distance was confirmed. Larvae (especially the first and second instar)took a comparatively long time to consume aphids and, in the field, one of them was prevented from feeding on an aphid colony by the attacks of ants which were tending them. The behaviour of larvae is discussed inrelation to their survival in the field. It is considered likely that in areas of low prey density many larvae (especially newly-hatched ones) die of starvation because they do not find aphids.