It could be delayed but that also depends on how warm it will be after the winter. So if it will be quite warm everything could be normal or they could even fly earlier. What species do you mean exactly?. For Camponotus species like Camponotus ligniperda the longer winter won't have any real impact since the alates hibernate in the nest so their development can't be delayed since they are already developed. Other species do hibernate with alate brood so the development of this brood could be getting delayed.
Lasius niger flies from mid-June up to the beginning of September according to Seifert's book (Ameisen Mittel- und Nordeuropas, Ants of middle and northern Europe) so they always have a range in which they fly not a specific month at least most species.
Edited by Barristan, March 11 2018 - 12:26 PM.