Abstract

Experiments were carried out to investigate the egg-laying behaviour of the maize weevil, Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) in uninfested and previously infested (termed conditioned here) maize grains. The number of offspring produced and preferred grain type of the weevil were examined under laboratory conditions, along with the effect of the presence of egg plugs on the oviposition site selection. The number of progeny produced was higher in conditioned maize. The highest and lowest number of adults emerged from conditioned and uninfested maize, respectively. S. zeamais individuals were significantly more attracted to conditioned grains compared to uninfested grains. S. zeamais females laid more eggs on host grains already bearing conspecific eggs (that is, conditioned) compared to clean grains (that is, uninfested). The number of eggs per grain showed a contagious distribution because females laid additional eggs on grains already infested with more than one egg. The results of this study indicate the possible role of the aggregation pheromone, intraspecific competition and egg marking in the observed egg-laying behaviour pattern of this pest species.

Key words: Maize weevil, egg, aggregation pheromone, oviposition behaviour, host marker.