Estudos morfológicos e comportamentais do parasitoide Bracon vulgaris Ashmead (Hymenoptera: Braconidae).

Abstract

The biological control of the boll weevil in Brazil is realized mostly by insect parasitoids, in which Bracon vulgaris Ashmead, a gregarious larval ectoparasitoid, is the most important biocontrol agent responsible for natural reduction of boll weevil populations in cotton ecosystem in the Northeast of Brazil. Even though it has a major importance in cotton production, there is no much data referring to parasitism of A. grandis by B.vulgaris, such as the effect of age, photoperiod and host availability in the parasitism behavior of this braconid wasp, as well as the morphological mechanisms involved in the parasitoid-host interaction. Therefore, this study investigated the morphological components involved in the success of parasitism of boll weevil by B. vulgaris, and the effects of age, photoperiod and host availability in the parasitism behavior of this natural enemy. Through techniques of scanning electron microscopy that the B. vulgaris ovipositor is a multifunctional structure whose composition and morphology are closely related to the role they play, and the parasitoid’s antennae present four types of sensilla (trichoids, basiconical, coeloconical, and placodes) that act as olfactory and gustatory receptors and or express tactile, therm, and hygro-reception functions. Behavioral tests showed that female five days old, the shortest time to host location occurred 8h after light exposure, when parasitoids were most active searching for the host. In relation to the behavioral repertoire of parasitism, B. vulgaris showed the sequence of following behaviors: host search, static, grooming, host acceptance, oviposition and resting. An associative evaluation of the morphology of sensory structures and behavioral studies allowed the better understanding the high rates of parasitism presented by B. vulgaris on A. grandis.