Just wondered if a female that has not been mated, and has already started laying ootheca, can still be mated so that all the subsequent ootheca are fertile?
She certainly can. Although species such as Brunerria and on some occasions, Taumantis will produce fertile ootheca without mating, through parthenogenesis.
lol last fall i got eggs (chinese off of ebay) and it came with a sheet that said it will hatch mated or not they said they were parthenogenetic but i was smart not to fall for it.
If she wasn't mated then the ooth is not going to hatch. But if she is already laying ooths and then you mate her the ooths laid after the mating will be fertile.