oa African Entomology - Pre-winter settling by prepupae of a seed-feeding weevil Rhyssomatus marginatus Fihraeus (Coleoptera: Curculionidae), a biocontrol agent of Sesbania punicea (Cav.) Benth. (Fabaceae) in South Africa
During autumn, prepupae of Rhyssomatus marginatus Filhraeus (Coleoptera: Curculionidae) leave the seed pods of their host plant, Sesbania punicea (Cay.) Benth. (Fabaeeae), and burrow into the soil where they settle for the duration of winter. In the field, most of the dormant prepupae were found at depths of between 10 and 20 cm, while none were found deeper than 30 cm. In the laboratory, most prepupae were unable to burrow into dry soil. The prepupae only emigrated from pods that had been soaked, a response which ensures that the prepupae avoid dry soils. The prepupae burrowed at the same rate and settled at similar depths in moist sand and clay. In soils with alternating layers of coarse and fine particles, most prepupae settled among the fine particles. There are no indications that pre-winter settling by prepupaeof R. marginatus is adversely affected by conditions in S. punicea habitats in the southwestern regions of South Africa.
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