Abstract
Dormancy is described for adults of the stalk-eyed fly, Diopsis longicornis Macquart (Diopsidae: Diptera) in the tropical savanna of coastal Guinée, 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.
Résumé
La période de dormance est décrite pour le stade adulte de Diopsis longicornis Macquart (Diopsidae: Diptera) un ravageur de riz de la savanne tropicale guinéenne de l’Afrique de l’Ouest. Les populations de diopsidés ont demeuré dans leurs sites de refuge respectifs pendant la saison sèche sauf dans les sites qui se sont assèchés. Le rapport male: femelle est demeuré stable pendant ce stade de dormance reproductive. Le taux de femelles était légèrement plus élevé (56%) et de celles-ci seulement 0.8% portait des oeufs. À la fin de la saison pluvieuse, la migration de D. longicornis depuis les champs de riz vers les sites de refuge coincide avec la récolte de cette culture (fin octobre et novembre); par contre les diopsidés quittent ces sites en fin de saison sèche (mai et début juin) bien avant le début de la prochaine campagne de riz (juillet et août) en saison pluvieuse. Ces insectes ont maintenu leur période d’arrêt reproductif en saison sèche même en présence de leur plante-hôte, le riz. Les plantes-hôtes secondaires de D. longicornis ont également été évaluées au cours des deux saisons climatiques pour leur importance comme sites de ponte et de sources de nourriture.
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Chiasson, H., Hill, S.B. Dormancy in the Stalk-Eyed Fly, Diopsis Longicornis Macq., a Pest of Rice in Sub-Saharan Africa. Int J Trop Insect Sci 16, 303–310 (1995). https://doi.org/10.1017/S174275840001732X
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DOI: https://doi.org/10.1017/S174275840001732X
Key Words
- Diopsis longicornis
- Diopsidae
- Diptera
- dormancy
- tropical savanna
- refugia
- rice stemborer
- secondary host plants
- West Africa