DIPLOID MALES IN THE BUMBLE-BEE BOMBUS-TERRESTRIS SEX DETERMINATION, SEX ALLELES AND VIABILITY

The frequency of colonies that produce diploid males after brother-sis ter (50%) and nephew-niece (37.5%) matings proves that in B. terrestri s the sex is determined by a single multi-allelic sex locus. The diplo id males which develop normally into adults make up 50% of the diploid brood. In the laboratory the growth rate of colonies with diploid mal es is influenced only slightly. Of 41 colony founding queens caught ou t of a natural population, all produced a colony without any diploid m ales. Therefore, the number of sex alleles in this population is estim ated to be at least 24. This means that in commercial rearing systems for bumble bees, involving several generations, the occurrence of dipl oid males can largely be prevented by a good scheme for crossings.