Can female Drosophila melanogaster lay eggs without males? Can female _Drosophila melanogaster_ lay egg without males? I maintain our lab stock but find a line that seems to have all females (or all males). The flies have been in the vial for two weeks, but I don't see any eggs hatching or become larva.

Yes, I regularly have to collect female virgins (12500 of them in the last week). They will lay eggs especially when there is extra yeast available. It is actually a good way to check virginity (in case a fly hatched early and was already mature, or a male made it through sorting etc.) - put some extra yeast grains in the vial when you collect them, leave them for a few days and then check for larvae, if they are not virgins there will be eggs and larvae, if they are virgins there will only be eggs!