Offspring produced by sib-mated queens.

A quarter of the offspring were diploid males, which do not produce functional sperm (S1 Fig). By contrast, no diploid males were produced by 17 queens mated to males from other populations. Confidence intervals were computed using a one-sample proportion test. Except for one colony, where the queen died prematurely, all others produced diploid male ratios not significantly different from the 25%, which is expected under a two-locus sex determination model, but different from the 50% expected under a single-locus model.* The queen died about one month into the experimentOffspring produced by sib-mated queens.