Changes in learning ability and mechanism during development of grasshopper nymphs, Melanoplus bivittatus

Abstract

Abstract. In an experimental arena, Melanoplus bivittatus (Say) (Orthoptera: Acrididae) nymphs of four stadia were observed to determine whether they learn to associate food with positional or light‐related cues. Nymphs were observed for 4 h in the arena containing one yellow box and one green box, then they were trained by placing food in the green box overnight. Following training, the responses of nymphs to green and yellow boxes were observed for a second 4 h period.Before training, nymphs of all stadia visited the yellow box more frequently than the green box. Training did not affect the behaviour of second‐stadium nymphs, but training increased the relative frequency of visits to the green box by third, fourth and fifth instars. Effects of training on duration of visits to boxes were not evident. Investigations of the mechanism of learning showed that positional cues were used by third‐stadium nymphs, but that fourth and fifth instars responded to light‐related cues. The progression from no learning in second instars, through use of positional cues by third instars, to use of light‐related cues by fourth and fifth instars is probably associated with the greater mobility, greater food consumption, and more varied diet of older nymphs.