For some invertebrates it is a form of sex determination: males are produced parthenogenetically, while diploid females are produced biparentally from fertilized eggs. In the case of the honeybee, the queen stores sperm and can lay both fertilised and unfertilised eggs. The unfertilised eggs developed into haploid drones by arrhenotoky.
Roger I. C. Hansell; Margaret M. Mollison; William L. Putman (1964). "A cytological demonstration of arrhenotoky in three mites of the family Phytoseiidae". Chromosoma15 (5): 562–7. Springer Berlin / Heidelberg. doi:10.1007/BF00319990. ISSN0009-5915.