Egg survival strategies of the Senegalese grasshopper during the dry season in the African Sahel

Abstract

The Senegalese grasshopper is a major pest of crops in Sahelian Africa. It has three generations per year and undergoes a 7–8-month long embryonic diapause during the long dry season. Egg pods collected at the end of the rainy season from mid-August to the end of September (the known period of induction of the diapause) were placed in incubation in semi-natural conditions, and were humidified on various dates between November and August. The results reveal a rather complex diapause system, which is undoubtedly part of a bet-hedging strategy that is well adapted to maximizing overall survival and reproduction in the variable rains of the Sahel. In this strategy, some eggs hatch on early wet season rains and survive well if there is follow-up rain, while others remain in diapause and hatch when the wet season is assured.

Keywords:

• diapause
• egg development
• grasshopper
• quiescence
• survival strategy

Acknowledgements

We are very grateful to the PRéLISS Project and the Danish Cooperation (DANIDA), respectively, for their technical and financial support during this study, and the AGRHYMET Regional Centre of CILSS for permission to work in the insect rearing rooms and for the assistance of the staff. We also would like to thank Dr Mark Jervis, Dr Dave Hunter and two anonymous reviewers for their useful comments improving the manuscript.