While the sightings have sparked excitement from wildlife enthusiasts, Mr Williams is not optimistic about their future.
One of the plants they feed and lay eggs on – the great water dock – is present at the reserves, but he does not believe there is enough to sustain the species, and also believes the area is too small for them.
“It requires a very very large area of habitat to be successful and we haven’t got that in the Black Country. It’s not enough to sustain them in the long term,” he said.
“Sadly I don’t think they’ll last in the Black Country. I think they will eventually die out.”
Mr Williams also claimed that British winters were not suited for the butterflies, and that they might perish over the winter.
Speaking about their release, he added: “It’s far from a wise move. These releases hardly ever succeed.
“People shouldn’t take this into their own hands and release butterflies willy nilly.”