Formica aquilonia
Temperature
18–24 °C
Humidity
50–70%
Colony size
50,000–500,000
Queen size
9–11 mm
Worker size
4–9 mm
Hibernation temp
5 °C
Diet
Care Guide
Formica aquilonia is a striking species of wood ant native to northern Europe and Asia, known for building large, thatched mounds in forests and dominating entire territories with colonies that can exceed half a million workers. The queen, measuring 9 to 11 mm, is sleek and dark with a subtle reddish hue, while workers range from 4 to 9 mm and show a slight size variation between minor and major individuals. What truly sets this species apart, however, is its parasitic founding strategy. A newly mated queen does not start her colony independently. Instead, she infiltrates a host colony—typically from the *Formica rufa* group—kills or subdues the resident queen, and then uses the host workers to raise her first generation of offspring. Once her own workers emerge, they gradually replace the host population, and the colony becomes a pure *Formica aquilonia* supercolony.
This parasitic founding method makes *Formica aquilonia* a challenge even for experienced keepers. The queen requires a suitable host colony fragment to be introduced, and the process is delicate—failure to accept the foreign queen is common. Once established, though, the colony grows rapidly and can become impressively large, demanding a spacious formicarium with a well-ventilated foraging area. These ants are highly active, diurnal, and thermophilic, preferring temperatures between 18 and 24°C with humidity around 50–70 percent. They require a true winter diapause at approximately 5°C for several months; skipping hibernation can severely weaken or kill the colony. Their diet should be rich in protein from insects and supplemented with sugar water or honeydew. They also appreciate natural sources of honeydew, so offering a live aphid culture can be rewarding.
Care difficulty
Keeping *Formica aquilonia* is suited only for advanced keepers. The parasitic founding stage is the main hurdle—without a host colony or a carefully managed introduction, the queen will not survive. Even after establishment, the colony’s enormous potential size and need for a large, cool hibernation space require considerable planning and resources.
Housing
Because these ants build substantial mounds in nature, they need a formicarium with deep nesting chambers and a large arena. The nest should be kept in subdued light, as the ants are sensitive to disturbance. Maintain separate hydration zones to create a humidity gradient, and ensure the foraging area is escape-proof—these ants are strong climbers and will exploit even tiny gaps. During the active season, offer a heat spot up to 24°C, but allow cooler areas for the colony to regulate.
First days after purchase
Upon receiving your *Formica aquilonia* colony, place the setup in a quiet, dim location. Do not disturb the ants for at least three days. If you received a founding unit with a queen and host workers, avoid opening the container to inspect; simply provide a drop of sugar water and a small insect piece near their entrance. Check that humidity levels are adequate and that the ants have begun to settle. Any excessive stress during acclimation can cause the queen to be rejected or killed, so patience is essential. Once the first workers of *Formica aquilonia* appear, you can gradually begin regular feeding and observe the fascinating transformation of a parasitic colony into a self-sufficient powerhouse.