Formation of long-term olfactory memory in the cricket Gryllus bimaculatus.

Insects live in constantly changing environments, where the availability of food sources varies with the seasons. Therefore, the ability to learn to associate a certain cue with an abundant food source must be of great significance for insects (Mizunami et al., 1999). However, most previous studies on olfactory learning in insects have been restricted to the honey bee Apis mellifera and the fruitfly Drosophila melanogaster. It is obvious that studies in only two species are not sufficient to understand fully the principles of olfactory learning and its neural mechanisms. Recently, we found that the cricket Gryllus bimaculatus (Matsumoto and Mizunami, 2000) and the cockroach Periplaneta americana (Sakura and Mizunami, 2001; Sakura et al., 2002; Watanabe et al., 2003) have a developed capacity for olfactory learning. Here we review recent progress on the olfactory learning capabilities of the crickets, which provide a solid basis for future studies of neural mechanisms of olfactory learning and memory.