Drones produced from their unfertilized eggs are genetically the same as if she were a queen. Cordovan Italian queens are easier to find in a hive. The presence of only cordovan drones in a hive confirms the presence of a cordovan queen. Hygienic behavior Hygienic behavior is expressed by bees uncapping and removing diseased brood. Recessive genes are expressed only if the dominant version is absent.
Bees carrying a recessive gene can pass it on without expressing the trait.
Only one dominant allele is necessary for expression of resistance. The mechanism of resistance is not known for certain. There is evidence that grooming behavior is involved. If a fertilized egg has two of the same sex alleles, it is not viable. These diploid drone larva are eaten by workers as the egg hatches.