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Well, you guys might be right, because I forgot the possibility that there could be other Chalcosyrphus species in the nearctic who look like piger (like this one does) but are a bit different.
This is what Chalcosyrphus piger in the nearctic seems to look like:
http://bugguide.net/node/view/26492
And indeed it has a different leg color, but also, in my opinion, very dark wings!
greetings,