Formica ulkei are the largest variety of Formica which live in Canada. These are the largest of Formica with queens from 8-10 mm and workers from 6-10 mm. Mature colonies will accept new queens, becoming polygynous and allowing them to grow extremely large colonies up to 100,000 workers in 10+ years. They prefer 22-26 Celsius and like around 50% humidity, though there is slight variation across species. They're more skittish than most ants, and so are of medium difficulty to start, but are extremely enthusiastic and fast growing once they break 50 workers. In the wild, Formica ulkei are the most dominant ants in their area, hunting down other species and consuming large amounts of biomass. We get many of these each year, though the numbers are variable. Note that this species requires good ventilation, or their formic acid spray may become an issue.