What mechanistic factors affect thelytokous parthenogenesis in Apis mellifera caponises queens

The Cape honey bee (Capensis) is unusual in that workers can produce viable female offspring via thelytokous parthenogenesis. In contrast, mated queens never reproduce thelytokously, even though they could benefit from doing so when generating daughter queens. Nonetheless, virgin Capensis queens induced to lay without mating by CO2 narcosis produce a high proportion of thelytokous eggs, and instrumentally inseminated queens produce triploid offspring as the result of the fusion of two egg pronuclei and a sperm nucleus. We show here that thelytoky/triploidy in Capensis queens is not a consequence of CO2 narcosis per se because narcosis of laying queens does not induce thelytokous or triploid progeny. We also show that in artificially inseminated queens, the frequency of thelytoky/triploidy declines with age and is absent 10 months post-insemination. We confirm that the presence of semen in the spermatheca is not the mechanism that prevents thelytoky/triploidy in mated queens.