The larvae of Mussidia nigrivenella Ragonot, attack various fruits; it is the main maize cob borer in Ivory Coast. The development of attack during the cultivation, the behaviour of larvae in the field, the spatial distribution of eggs and larvae, the mortality of pre-imaginal instars and the annual fluctuations of populations are considered in this paper. This insect may represent an economical problem for seed producers in the south of the savannah area of Ivory Coast where its density exceeded 14 insects per cob, at harvest in 1984, whereas the risk of cob damaging by Mussidia nigrivenella appears to be very weak in the north and west of this region.
