SummaryMutant queens were mated instrumentally with their brothers of wild or mutant genotype, and 20 queens producing scattered brood were chosen for further investigation.Phenotypes of haploid drones, and of workers originating from those queens, were determined. Using the method for rearing diploid drones, 691 drones were reared from eggs laid in worker cells. Participation of the father, as well as the exclusion of androgenesis or parthenogenesis, was demonstrated in some of these drones. Mating of 5 queens homozygous for one mutant gene with brothers mutant for another gene allowed 302 drones of wild phenotype to be reared, proving genetically their biparental origin.