Uncapping of pupal cells by European bees in the United States as responses to Varroa destructor and Galleria mellonella
Alexis J Villegas and José D Villa
We investigated the uncapping of pupal cells by honey bees in the United States as responses to infestation with V. destructor and G. mellonella. In a group of 15 colonies, we counted the number of uncapped cells with pupae, and estimated the total sealed brood area. At the same time, the infestation by V. destructor and evidence of wax moth activity were measured in uncapped pupal cells, in cells immediately adjacent (neighbours), and in cells along linear transects. The relative amount of uncapped pupal cells (uncapped pupal cells/total sealed cells) increased with infestation (linear regression R2 = 0.64, slope = 0.16). Varroa mite infestation of uncapped cells (30%) significantly exceeded that of neighbours (14%) and also that of transect cells (12%), but infestations of neighbour and transect cells were similar. The relationship between infestation of uncapped cells and that of other cells (neighbour or transect cells) had a slope significantly higher than one, suggesting that discrimination of infested cells increases with overall colony infestation. Frequencies of wax moth activity (presence of larvae, frass, tunnelling and webbing) were highest in uncapped cells (33% ), lower in neighbour cells (21%) and extremely low in transect cells (4%).We followed the opening, removing and resealing of pupal cells every 24 h in a colony with one of the highest infestations with varroa mites and with one of the lowest levels of wax moths, and in a second colony with the opposite infestation levels. Many opened or partly removed cells were found in a different condition, suggesting a dynamic process under conditions of high infestation.