Although very Lasius-like (after all, Prenolepis belongs to the Lasiini tribe), these sexuals have no closed discoidal cell on the forewings. I could finally find them out thanks to a picture of a winged queen by Tony Di Terlizzi in this guide, where a blurry but recognizable worker is visible in the background.
A hard-boiled feminist would tell you that a male IS anyway "some type of parasite" for the female, whatever the species :-)

They are indeed a male and female mating. You can see why male ants (the small one) are often not preferred for identification - they are so small and the taxonomy is based primarily on the females/workers. My guess is Lasius neoniger. Stefan Cover at Harvard could probably tell you in a split second.

Mating would be my vote Tom,

Check this out, I think I have shot similar species here:

...and here: