Dear Kelley, The higher rate of brood cell invasion into drone cells by Varroa mites can partly be explained mechanically. When you consider that a mite has to be brought by a bee to a suitable brood cell, the almost two times bigger area of the drone brood cell will attribute to this higher rate. Moreover, drone cells are already invaded from more than two days before the brood cells are capped, while worker brood cells are invaded from about 1/2 a day before capping. In this way a higher drone brood cell invasion rate of about 8 times can be expected. However, drone brood cells are invaded at a 12 times higher rate compared to worker brood cells. A qualitative or quantitative chemical difference may explain the yet unexplained part of the higher invasion rate into drone brood cells. yours, Johan Calis [log in to unmask] Wageningen Agricultural University The Netherlands