Bees create distinctive microenvironments by constructing cell within nests, where they lay eggs on pollen and nectar (Odling-Smee F.J. et.al. 2003. Niche Construction). Each cell inside the nest is a miniature ecosystem, and the stored food is favorable not only for the development of their own brood, but also for an extensive array of organisms. The most common arthropod symbionts living inside social insects’ nests are mites (Acari, Arachnida) (Eickwort C.G. 1990. Annual Review of Entomology, 35, 469-488).

Hitherto, most of the research on this subject has focused on social bees, or is largely limited to taxonomic and systematic studies, however, the nature of the symbiosis has not been investigated rigorously (Eickwort C.G. 1979. Recent Advances in Acarology: 575-581). Our objective was to assess which kind of symbiosis is the one established between the socially polymorphic genus Megalopta (Halictidae) and its associated mites.   

In 2005, we collected nests of two sympatric species M. genalis and M. ecuadoria in the tropical forests of Panama. We scanned cells, bees and nest substrate under a microscope for the presence of mites and fungi. Interestingly, the cells containing mites are significantly less likely to contain detrimental fungi than cells without mites (n=87, p<0.0258).  We hypothesized that mites reduce infection by directly feeding on the fungal spores.

Furthermore, there is no significant association between the presence of mites and the sex of the pupa in the cell (X² n=24, p>0.52) meaning that mites cannot differentiate the sex of the bee egg. Likewise, there is no correlation between the presence of mites and the social organization of the nest, so solitary and social nests have the same likelihood of possessing mites (X² n=53, p>0.1998). If sustained with additional data, it will be the first demonstration of a mutualism in bee-mite associations.