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
 
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Wageningen Agricultural University
The Netherlands