Self-grooming behavior of <em>Aedes aegypti</em> exposed to <em>Metarhizium humberi</em> formulation

Aedes aegypti L. (Diptera, Culicidae), the key vector of viral diseases to humans in the tropics, is susceptible to infection with entomopathogenic fungi. Self-grooming behavior, which has still been little studied in mosquitoes, may possibly interfere with fungal infection through the cuticle. In this study, self-grooming by A. aegypti adults exposed to Metarhizium humberi Luz, Rocha & Delalibera 2019 (Hypocreales, Clavicipitaceae) conidia mixed or not with micronized carnauba wax (MCW) led to a decrease of non-germinated conidia and early germinating stages from their body surface up to 24 hours after exposure to a fungus-treated surface. Adults showed a low-level, spontaneous, and stimulus-independent self-grooming behavior that was distinctly increased after exposure to conidia mixed or not with MCW or solely to MCW. The first pair of legs scraped synchronously the proboscis, antennae, and wings; legs of the third pair scraped each other as well as synchronously the first and second pairs of legs, and the gonapophyses. Conidia, mixed or not with MCW, or MCW were readily detected on tarsi, tibias, and femurs, especially of the first and second leg pairs, gonapophyses, proboscis, antennae, and wings, immediately after exposure. In mobile adults, mean conidial numbers dropped approximately fivefold in the 24 hours immediately following exposure, especially in the first 6 hours, regardless of the conidial preparation, and then, to a lesser extent, in the remaining 18 hours. Conidial loss was distinctly lower or insignificant in cold-immobilized individuals in the same period. MCW did not increase the number of conidia on the cuticle or enhance their permanence on the cuticle during the tested period. These findings strengthen the importance of considering self-grooming of mosquitoes in particular A. aegypti, the vector examined here, when developing specific fungal formulations for biological control.