Formica lugubris
Temperature
18–24 °C
Humidity
50–70%
Colony size
50,000–400,000
Queen size
9–11 mm
Worker size
4.5–9 mm
Hibernation temp
5 °C
Diet
Care Guide
Formica lugubris, the “Silky Wood Ant,” is a captivating but challenging species best suited for experienced keepers. Unlike typical ant colonies that start with a lone queen raising her first brood, *Formica lugubris* is a social parasite. The young queen must locate an existing host colony—usually another *Formica* species—infiltrate it, and take over the nest, tricking or overpowering the host workers into raising her own offspring. This founding strategy makes keeping them an advanced endeavor, but the reward is a powerful, resilient colony that can grow to impressive numbers, often reaching hundreds of thousands of workers.
Workers in a mature *Formica lugubris* colony show notable size variation, with minor workers measuring around 4.5 mm and large major workers reaching up to 9 mm. The queen herself is a robust 9–11 mm. These ants are vigorous builders, constructing large thatched mounds in the wild, and they thrive on a high-energy diet. They are active hunters of insects, but also eagerly collect honeydew from aphids and enjoy sugar water. A consistent source of protein is essential for brood development, so offer a variety of feeder insects such as crickets, flies, and mealworms. They also appreciate diluted honey or sugar syrup.
Care difficulty
Keeping *Formica lugubris* is best left to intermediate and advanced ant keepers. The parasitic founding stage is particularly delicate: the queen must be introduced to a suitable host colony in a controlled way, and success is never guaranteed. Once the colony is established, care becomes more straightforward, but the sheer size potential (up to 400,000 workers) demands planning ahead. These ants are also fast-moving and can be skittish, so disturbance should be minimized.
Housing
Provide a formicarium with both a humid nest area and a drier foraging zone. Maintain temperatures between 18–24°C, with a slight drop at night. Humidity should stay between 50–70%; the nest section can be kept moister, but avoid waterlogging. *Formica lugubris* requires a true winter hibernation period. From late autumn, gradually reduce temperature to around 5°C for three to four months. Without this cold rest, the queen will stop laying eggs and the colony may decline. The foraging area should be large enough to accommodate thousands of workers, with a secure lid—these ants are excellent climbers and escape artists.
First days after purchase
If you have purchased a colony already established (post-parasitic phase), place the formicarium in a quiet, dim location and allow the ants to settle for at least 24 hours. Ensure the nest is slightly moist and provide a small drop of sugar water and a tiny insect piece. Observe from a distance; avoid vibrations and bright light. If you have purchased a parasite queen, follow specific introduction protocols carefully. In both cases, patience is key. Once the colony feels secure, you will be rewarded with the fascinating sight of a true woodland giant at work.