How to Care for Formica fusca | The Silky Ant Guide for Beginners
Updated: 3 days ago
Fast, alert and always busy, Formica fusca is one of the most exciting UK native ants to keep. The silky ant is big for a British ant, quick on its feet and a brilliant little hunter.
Drop food in the outworld and the workers race out to grab it. This guide explains Formica fusca care step by step, from the day your parcel arrives to a thriving colony of hundreds.
We have kept ants since 1997, and everything here comes from our own colonies and the care rules we use every day.
👉 In a hurry? Download our free Formica fusca care sheet (PDF) or open the Formica fusca care sheet page for the key facts at a glance.
Formica fusca at a Glance
Also known as: the silky ant, or Serviformica fusca
Origin: UK native, found across Europe and northern Asia
Keeping level: Beginner
Queen: 10 to 12mm, dark brown to black with a silky sheen
Workers: 4.5 to 7mm, all one size, dark brown to black
Colony: usually around 500 workers, a few thousand when large
Nest temperature: 20 to 26°C
Nest humidity: 50 to 70%
Workers before moving into a nest: 10 minimum, 15 to 20 recommended
Winter: hibernation optional
Escape risk: fast climbers, so a PTFE barrier is a must
Meet the Silky Ant
In the wild, silky ants nest in soil, under stones and in old tree stumps along woodland edges and hedgerows. Their dark bodies shine with a soft, silky sheen in the sun, which gives them their name.
They have no sting. When they feel threatened, workers can spray a tiny puff of formic acid, which is harmless to people.
Silky ants are also famous for another reason: they are the favourite "host" species of the slave-maker ant, Formica sanguinea, which raids their nests for brood.
New queens fly out to mate in summer, usually from June to August. A mated queen then seals herself in a small chamber and raises her first workers alone, living on her own body reserves.
When Your Ants Arrive
The most important step: leave the parcel completely unopened, exactly as it arrived, at room temperature for 5 hours. The ants must adjust to your home's temperature slowly, because abrupt temperature changes make ants seriously unwell.
After the 5 hours, check the queen is safe and sound. Then leave the colony in its original packaging, with the test tube still in its tin foil and wrapping, somewhere quiet and still, away from daily household activity.
Give the colony 4 to 5 days of complete rest. The ants were fed before dispatch, so they need nothing from you. Use this time to set up and water the nest. 👉 Our step-by-step ant farm setup guide shows you how.
Still workers or a motionless queen after delivery are almost always delivery stress. Look at the queen's antennae: moving antennae mean she is fine. Almost all recover within 4 to 5 days.
Life in the Test Tube
Keep the colony in its test tube until it has at least 10 workers. 15 to 20 is even better. Moved earlier, the workers often abandon the queen in the bigger space, and the colony can fail.
A queen on her own still needs a little food, even though she could survive on her reserves. Once a week, give her a tiny drop of protein jelly, about half a grain of rice, on a small flat piece of tin foil inside the tube, next to the dry cotton stopper.
In our experience a fed queen raises her first workers faster, and the queen and colony do far better afterwards. Keep her tube wrapped in its foil and disturb her as little as possible.
Moving Into the Ant Farm
When the colony is ready, connect the test tube to the nest with the delivery tin foil still on. Leave it like that for 14 days.
Then slide the foil back about 1mm every day until the tube is fully exposed to daylight. If the ants haven't moved 2 days later, wrap the foil back on, wait another fortnight and repeat. Moving in can take from a couple of days to 6 months.
Once the colony has moved, leave the old test tube connected for at least another 14 days, as ants sometimes leave brood behind.
The red filter and black cover stay on the nest all the time. You can lift the black cover once a day for 2 to 3 minutes, ideally at night, and take the red filter off once a week for 2 to 3 minutes.
The Best Ant Farm for Formica fusca
Silky ants grow fast and love to explore, so give them a nest with room to expand and a good-sized outworld. Every Best Ants UK ant farm suits them.
👉 Our top pick is the A7 Plus ant farm kit. Its pre-installed digital meter shows nest temperature and humidity at a glance, which keeps watering simple and mistakes to a minimum.
Place the ant farm in normal daylight, never direct sunlight. Avoid windows, radiators and heaters, vibrating surfaces, speakers and TVs, and rooms with strong smells such as the kitchen.
Temperature and Heating
Keep the nest at 20 to 26°C. In a warm home, normal room temperature is enough.
In a cool home, though, where the room stays around 20°C or below, the brood takes far longer to develop. 👉 There, an Advanced Heating System Small 4W set to 24°C helps the colony thrive.
The heat mat goes under one quarter of the nest only, on the side opposite the watering area, so the ants can choose their spot. Never heat the whole nest.
In the outworld, aim for about 18°C overnight up to 28°C by day. By day it should ideally match the nest or be a degree or two cooler. If the nest is heated, warm the outworld too, because a big gap confuses the ants.
Water and Humidity
Keep the nest humidity at 50 to 70%. Use distilled or purified water only. Never use tap water, rainwater or bottled mineral water, even boiled: they cause mould and fungus, which is deadly for ants.
Water the nest with the pipette provided. Pour slowly, a few drops at a time, through the watering hole. Stop as soon as 1 or 2 drops appear inside the nest. That is how you know it is done correctly.
Water about once a week, a little more in summer and a little less in winter. With a meter, simply water when the nest humidity drops below 50%.
Never water the outworld. Keep it dry, at about 50% humidity, like an average UK home.
Feeding Your Silky Ants
Silky ants are keen hunters, and a growing colony has a big appetite for protein. Feed twice a week, in small amounts, in the outworld only. Remove leftovers after 2 days to stop mould.
🥩 For the queen and brood, give 👉 Protein Jelly or 👉 Cricket Mash. Keep protein jelly in the fridge at all times.
🍯 For energy, give our 👉 organic ant honey or 👉 Ant Nectar, which has even more carbohydrates than honey. Both are far better than sugar water or home-made mixes.
Serve food on a small piece of tin foil or in a 👉 small feeding dish, so leftovers are easy to lift out.
Live food, such as crickets or locusts, is only for big, established colonies, never small ones. Always scald it first: wearing gloves, hold it with tweezers in just-boiled water (above 90°C, no longer bubbling) for 10 to 15 seconds, then cut it in half and serve it in the outworld.
Keep Mites Out of Your Colony
Blood-sucking mites are one of the biggest dangers for any ant colony, and they are not rare. They often arrive with bird seed from local shops, dried mealworms, and live food bought from pet shops or online marketplaces.
Buy ant food only from established, reputable ant-keeping suppliers. At Best Ants UK we clean our foods in several ways before dispatch, check every colony twice a month, and check each colony again before it leaves us.
Now and then, look at your queen with a magnifying glass. Tiny white or reddish specks on her joints and legs, together with ants dying fast, are a warning sign of blood-sucking mites.
Stopping Escapes
Silky ants are fast climbers, so escape prevention is a must. Paint a band of 👉 PTFE Fluon escape barrier around the top inner edge of the outworld lid. The ants slip off it and can't climb out.
PTFE wears off as the ants keep testing the same spots. For a small colony of up to about 100 ants, reapply it roughly every 4 weeks. For 300 to 500 ants or more, reapply it about every 2 weeks.
Never shake the bottle, because it foams. Roll it gently in your hands instead.
Winter Care
Hibernation is optional for silky ants. They can stay at normal room temperature all winter, and you don't need to do anything special. We never hibernate queens in their first year.
Their development still slows down from late autumn, whatever the temperature. Their biological clock can't be tricked.
A full hibernation is only safe at a steady 10°C, roughly from December to the end of March. That needs a specialised hibernation unit with precise temperature control. Never use a fridge, shed or garage.
Feed less in winter, but never guess. At 17 to 22°C, give about a third of the summer amount. At 22 to 26°C, give about half. In full hibernation, give fresh water only and no food.
Can I Release My Silky Ants?
We don't advise releasing a colony raised indoors, as it is unlikely to survive outside. If you can't keep your colony any more, 👉 visit our ant adoption page and let us know. We'll see whether we can take it in.
Frequently Asked Questions | FAQ
Is Formica fusca good for beginners?
Yes. The silky ant is a hardy UK native that grows fast at normal room temperature. Its workers are quick climbers, so a PTFE barrier on the outworld is essential.
Do Formica fusca sting or bite?
They have no sting. Workers can spray a tiny puff of formic acid, which is harmless to people. As with every ant, never handle them.
How many workers before moving Formica fusca into a nest?
At least 10 workers, and 15 to 20 is even better. Moved earlier, the workers often abandon the queen in the bigger space.
What temperature do silky ants need?
Keep the nest at 20 to 26°C. In a cool home where the room stays around 20°C or below, an Advanced Heating System set to 24°C under one quarter of the nest keeps the brood growing.
Do Formica fusca need to hibernate?
Hibernation is optional. They can stay at room temperature all winter. A full hibernation is only safe at a steady 10°C, in a specialised hibernation unit with precise temperature control, never a fridge, shed or garage. We don't hibernate queens in their first year.
What do Formica fusca eat?
Protein Jelly or Cricket Mash for the queen and brood, plus organic honey or Ant Nectar for energy, twice a week in the outworld. Growing colonies are big protein eaters.
How big does a Formica fusca colony get?
Usually around 500 workers, and large colonies reach a few thousand. Most colonies start with a single queen.
Start Your Own Silky Ant Colony
👉 Find Formica fusca queens and colonies in our shop, and enjoy one of the busiest, most rewarding UK native ants.
Print this guide and keep it next to your ant farm. 👉 Keep the essentials close and explore all our free ant care sheets.
