Zabrotes subfasciatus Boh. (Coleoptera: Bruchidae) is the smallest of the bruchids commonly infesting stored legume seeds, yet its wild and cultivated hosts, Phaseolus lunatus and P. vulgaris, have large seeds. It is demonstrated that the maximum fecundity of females is around 55 eggs which are aggregated onto some of the available hosts. About 80% of the eggs normally hatch and development at 27 °C and 70% relative humidity takes around 34 days. The sex ratio of emerging adults is slightly biased towards males. About 75% of the larvae in a seed produce adults at low and moderate initial densities and up to 20 adults can emerge from a single seed. Adult weight is not influenced by the initial larval density in the seed but there is a strong correlation between the weight of females at emergence and their fecundity. These results are considered in the light of existing knowledge of Z. subfasciatus, much of which is apparently contradictory or inconsistent. Many of these difficulties are resolved and it is demonstrated that the behaviour and bionomics are well adapted to the normal situation in which the beetle is found and that the differences between this species and other bruchids are explicable in this context.
Pitfall traps baited with a lure containing a new pheromone component were used to catch adult Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in the field in Tanzania. Traps baited with a mixture of Trunc‐call (T1) and the new component Trunc‐call (T2) caught ten times as many insects as traps baited with T1 alone. The data demonstrate for the first time that mixtures of T1 and T2 can be used as effective lures to trap P. truncatus in the field, and that P. truncatus is widespread outside of farm buildings in Africa.
Résumé
Piégeage avec des phéromones synthétiques de Prostephanus truncatus dans des champs de maïs
Des pièges contre P. truncatus Horn, appâtés avec un leurre contenant une nouvelle phéromone ont été utilisés dans la nature en Tanzanie. Les pièges appâtés avec un mélange de Trunc‐call 1 (T1) et du nouveau composé Trunc‐call 2 (T2) capturent 10 fois plus d'insectes que ceux appâtés avec T1 seul. Ces résultats montrent pour la première fois que des mélanges de T1 et T2 peuvent être utilisés efficacement pour leurrer P. truncatus dans la nature, et que P. truncatus est abondant autour des fermes en Afrique.
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