Because, in likelihood, you're getting something else which the seller misidentified, else they obtained a Lasius niger colony illegally. Lasius niger (or similar, unnamed species) do exist in North America, but live so remotely -- I have my doubts that hobbyists would be able to find it. It's also notoriously confused with every black ant and the four other niger-group Lasius. If you have a legitimately sold Lasius niger colony, good on you!
Hibernation is important to the internal clock of the temperate workers, brood, and queen. Their colonies tend not to do well when they aren't put in the cold. Activity (foraging, egg laying, etc.) also tapers off during the hibernation period, regardless of the temperature.
Edited by Batspiderfish, July 25 2017 - 11:04 AM.
If you've enjoyed using my expertise and identifications, please do not create undue ecological risk by releasing your ants. The environment which we keep our pet insects is alien and oftentimes unsanitary, so ensure that wild populations stay safe by giving your ants the best care you can manage for the rest of their lives, as we must do with any other pet.
Exotic ants are for those who think that vibrant diversity is something you need to pay money to see. It is illegal to transport live ants across state lines.
----
Black lives still matter.
