Erick Provost

Resistance of the honey bee, Apis mellifera to the acarian parasite Varroa destructor: behavioural and electroantennographic data

Abstract. One way in which Apis mellifera honey bees resist Varroa destructor is by detection and elimination of nestmates. This study uses behavioural tests and electroanntennography to assess the role of chemostimuli in recognition by honey bees of this acarian ectoparasite. Behavioural tests using living or dead parasites involved observation of honey bee grooming activity (antennation) under controlled conditions in Petri dishes, and removal behaviour (uncapping and elimination of parasitized and unparasitized control brood cells) under natural conditions. Some bees from colonies with both small and large parasite populations showed aggressive behaviour (biting). No difference was observed according to whether the mite was dead or alive. Under natural conditions, bees uncapped more parasitized cells than control cells. Electroantennographic tests were performed to measure sensitivity to various Varroa extracts at three concentrations (10, 20 and 30 Varroa Equivalents). Only 30 Varroa Equivalent methanol extracts made from Varroa collected from brood cells elicited significantly greater antennal response than controls (pure solvent). All three methanol extracts elicited significantly greater antennal response than controls. No response was observed using Varroa extracts made with acetone or hexane. These findings suggest that polar products may act as chemostimuli for recognition of V. destructor by honey bees. Further study will be necessary to determine which polar products are involved in this recognition and assess grooming and removal behaviour using these products.

Floral Chemical Signatures in the Genus Ophrys L. (Orchidaceae): A Preliminary Test of a New Tool for Taxonomy and Evolution

Ophrys flowers sexually swindle male insect pollinators that cross-pollinate flowers during acts of pseudocopulation on the labellum. Classification of this species-rich genus into a natural system is difficult, even with the present molecular methods, because of low interspecific genetic variability. We investigated the potential for flower chemical signatures generated from gas chromatography of Ophrys labellum extracts to distinguish taxa and indicate phylogenetic relationships. Labellum extracts of five taxa from southeast France belonging to the sections Araniferae and Pseudophrys were analyzed. We obtained a high variability among all individuals with a good discrimination among all species. We conclude that lipidic compounds on Ophrys labellum represent species-specific chemical signatures, as has proven useful in insect taxonomy. Furthermore, a possible population effect is detected for a poorly described, polytypical species. We conclude that chemical investigations should be continued to clarify the classification of closely related taxa and to better understand the evolutionary processes in this extraordinary genus.