Dormancy in the stalk-eyed fly, Diopsis longicornis Macq., a pest of rice in sub-Saharan Africa

Abstract

Dormancy is described for adults of the stalk-eyed fly, Diopsis longicornis Macquart (Diopsidae: Diptera) in the tropical savanna of coastal Guinee, West Africa. Populations of diopsids maintained themselves within each chosen refugium throughout the dry season unless the site dried up. Sex ratio within the populations at each refugium remained constant throughout the dry period. Slightly more females than males were found (56%), and of these only 0.8% were gravid. Movement of stalk-eyed fly adults from the rice field to the refugia corresponded with the end of the rice cropping period (stage of ripening and harvest) at the end of the wet season (late October to November), whereas movement from the refugia to the rice field occurred towards the end of the dry season Gate (May/early June), but well in advance of the rice crop planting (July and August) of the following wet season. Insects retained their state of reproductive arrest in the dry season even when offered suitable oviposition sites, i.e. rice plants. Secondary host plants were investigated as possible oviposition sites and food sources for adult flies.