F. Ruttner wrote in his book "Biogeography and Taxonomy of Honeybees" on page 150 "Hetterospecific instrumental insemination of A. mellifera and A. cerana (with semen of the reciprocal species) is feasible: spermatzoa enter the spermateca ... No hybrid lava or imago developed in these experiments (Ruttner and Maul 1983 Experimental analysis of reproductive interspecific isolation of Apis mellifera L. and Apis cerana Fabr. Apidologie 14: 309-327) Personaly I think A. mellifera has to go its one way to find a coexistence with the varroa mite. Only about 3/5 of the A. mellifera genome is similar the DNA of A. cerana. So A. mellifera may have to develope its one defence mechanism and cannot copy these of A. cerana. Andreas Hdhnle