Heterosis in the Honey Bee (Apis Mellifera L.).

HERE are three castes in the honey bee colony: the drone, queen, and worker. T The latter two are both females. The drone bee is a male, representing a haploid gamete of the queen bee heading his hive. The honey bee colony is composed of two generations of bees. The queen bee is, in effect, a potent egg-laying machine, while the workers are morphologically and functionally fitted for honey and pollen gathering and for most other work of hive and field, except that under normal circumstances they do not lay eggs. The queen bee is the parent mother of the colony, and the worker bees are her progeny. Breeding methods to insure heterosis have led to increased vigor and productivity in corn, sorghum, Drosophila, poultry and other species. These species are diploid in both sexes. It is of interest to examine another species, having a different system of reproduction, for heterotic effects and to analyze for the responsible mechanisms. In this study hybrid vigor is regarded as the superiority of the hybrid over the better parent. The characters chosen for study are egg production of the queen, a character largely dependent on the queen’s own genotype, and honey yield, a character dependent on the vigor and well being of the queen’s worker progeny. Honey yield consequently differs from egg production in being influenced by the genome of the drones to which the queen is mated. The single queen will contribute a genome to each of the 50 or 60 thousand workers making up the colony. In the past the honey bees must have been intensely selected for the capacity to produce large numbers of progeny and workers active in gathering food supplies. The individual worker bee lives about 6 weeks during the active summer season. Rapid replacement of this worker force depends on the egg laying of the single queen mother. For existence the colony must harvest sufficient nectar in six to ten weeks to last the balance of the year. Till recently, numbers for egg laying and colony replacements have been rather vague, 200 to 5000 eggs per day were estimated. NOLAN (1923) has presented data indicating that rates of less than 2000 eggs per day over a 12 day period were to be expected. Larval deaths will reduce the effective worker groups. The effective oviposition rate will be less than the observed eggs laid, the actual oviposition, by any genetic or other factors favoring the death of the larva. In the inbreeding necessary to the formation of the inbred lines utilized in this study hypothesized sex alleles could be factors in this loss of larvae. MACKENSEN (1951), using brood viability counts, has postulated for the honey bees a series of haploviable alleles which are lethal in homozygous diploid females. However, earlier work of CALE (1952) indicated that the oviposition rate of inbred queens was independent