My .02 from this year's experience is that marking virgins is a waste of time. Can it be done with no harm to the queen, sure. But what's the point if she doesn't get mated properly at the end? I'd rather spend the effort marking after the confirmed results. Also, as others have stated, you might be adding that little bit of flash that does her in with a bird. Besides, after marking the first 4 virgins of this year and only getting one successfully mated, again, more trouble than it's worth.