Floral biology of Tropaeolum majus L. (Tropaeolaceae) and its relation with Astylus variegatus activity (Germar 1824) (Coleoptera: Melyridae)

摘要

Tropaeolum majus L. (nasturtium) is a culture popularly known by its medicinal, ornamental and culinary utility. This work aimed to evaluate the interaction between Astylus variegatus (Germar 1824) (Coleoptera: Melyridae) and the nasturtium flowers associated to the weeks of flourishing, in order to conceive the floral mechanisms used by the species to attract A. variegatus. The insects collection was achieved with an entomologic net by the sweeping method, during the weekly flowering, at two hours, from 7am to 5pm. The studies of floral biology were carried out in twenty flowers by the analysis of measures and the arrangement of the floral parts. The nasturtium flower offers pollen and nectar to the insect as a compensation. However, it was observed that A. variegatus only collects pollen as a nutritious resource. Tropaeolum majus presents several flowers for each individual and, during the visits, A. variegatus walked throughout the interior of the flower, among the stamens and contacting the ventral region of its body, and while passing through the stigma it lodged the pollen. Sometimes, it uses the internal cavity for sheltering and mating. The visits occurred preferably on the second and fifth weeks of flourishing, with a populational fluctuation between 9am and 11am.