How to Care for Formica sanguinea | The Blood-Red Slave-Maker Ant Guide
Updated: 3 days ago
Few ants have a story like Formica sanguinea. The blood-red slave-maker ant raids the nests of other ants, carries home their pupae and raises them as helpers. It is one of the most fascinating ants in Britain.
With their red heads and thoraxes and black gasters, they are handsome, bold and always busy. This guide explains Formica sanguinea care step by step, including how these unusual colonies begin.
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 sanguinea care sheet (PDF) or open the Formica sanguinea care sheet page for the key facts at a glance.
Formica sanguinea at a Glance
Also known as: the blood-red slave-maker ant, or Raptiformica sanguinea
Origin: UK native, found across Europe
Keeping level: Intermediate to advanced, not for a very first colony
Queen: 9 to 11mm, red head and thorax with a black gaster (back end)
Workers: 6 to 9mm, coloured like the queen
Founding: the queen needs workers of another Formica species to start a colony
Colony: can have several queens and a few thousand workers
Nest temperature: 21 to 24°C
Nest humidity: 50 to 60%
Workers before moving into a nest: 10 minimum, 15 to 20 recommended
Winter: hibernation optional
Escape risk: fast and bold, so a PTFE barrier is a must
Meet the Slave-Maker Ant
In the wild, Formica sanguinea loves warm, sunny places: heaths, dry grassland and forest edges. It nests in soil, under stones, in tree stumps and in dead wood.
Its raids are real expeditions. Scouts find a nest of another Formica species, often Formica fusca. Then a column of workers marches out, drives off the defenders and carries their pupae home.
Back home, the stolen pupae hatch into helper ants. These helpers have never known any other home, so they work for the raiders as if they were their own family.
They have no sting. When they feel threatened, workers bite and spray formic acid, which is harmless to people.
How a Slave-Maker Colony Begins
This is the most important thing to know before you buy. A Formica sanguinea queen can't raise her first workers alone, the way a Formica fusca or Lasius niger queen can.
In nature, a young queen walks into a small nest of another Formica species, such as Formica fusca. She takes over, and the host workers raise her first brood as if it were their own. Once her own red workers hatch, they start raiding for more pupae.
What this means for you: never try to start with a lone queen. Always choose a colony that already has workers. Don't be surprised to see some black workers among the red ones: those are the helper ants, and they are part of the family.
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 young queen with only a few workers still needs a little extra food. 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 well-fed queen raises new workers faster, and the colony does far better afterwards. Keep the tube wrapped in its foil and disturb it as little as possible.
From egg to adult worker takes around 10 weeks in warm conditions, so growth needs a little patience.
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. Take colony photos once a month at most.
The Best Ant Farm for Formica sanguinea
Slave-maker ants spray formic acid when disturbed. In a stuffy, sealed box it builds up and harms the colony, so their home must be well ventilated and spacious, with a good-sized outworld for hunting. Never block the air holes.
👉 Our top pick is the natural eco ant farm. It is airy and natural, and the ants can dig and build in it as they would in the wild. No connection is needed: take out the cotton stopper and place the test tube inside.
👉 For a young colony, the A7 Plus ant farm kit works well too. Its pre-installed digital meter shows nest temperature and humidity at a glance, which keeps mistakes to a minimum. If you already have your ants, choose the Nest + Outworld option.
These ants are sensitive to vibration and sudden changes. 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 21 to 24°C. Slave-maker ants love warm, sunny places, and warmth keeps the brood growing.
In a cool home, where the room stays around 20°C or below, they won't thrive and the brood takes far longer to develop. 👉 There, an Advanced Heating System Small 4W set to 24°C makes a big difference.
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 60%. 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%.
In the natural eco ant farm, water the surface of the substrate instead, 1 to 3ml at a time, and wait at least a day before adding more.
Never water the outworld. Keep it dry, at about 50% humidity, like an average UK home.
Feeding Your Slave-Maker Ants
Slave-maker ants are keen hunters with a big appetite for protein, and they do best on a varied diet. 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. In our experience about half of that live food carries mites.
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
Slave-maker ants are fast and bold, 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 Formica sanguinea. 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, and never make abrupt temperature changes.
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 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 sanguinea good for beginners?
Not for a very first colony. Slave-maker ants are fast, bold and hungry, and they need a roomy, well-ventilated setup. They suit keepers with a little experience. For a first colony, Formica fusca is an easier start.
Can a Formica sanguinea queen start a colony on her own?
No. In nature she takes over a small nest of another Formica species, such as Formica fusca, and those workers raise her first brood. That is why you should always choose a colony that already has workers.
Why are there black ants in my Formica sanguinea colony?
They are helper ants of another Formica species, raised from pupae the colony carried home or from the nest the queen took over. They work for the colony as if it were their own family.
Do Formica sanguinea sting?
They have no sting, but they bite and spray formic acid, which is harmless to people. As with every ant, never handle them.
How many workers before moving Formica sanguinea 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 Formica sanguinea need?
Keep the nest at 21 to 24°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 sanguinea 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.
Start Your Own Slave-Maker Ant Colony
👉 Find Formica sanguinea colonies in our shop, and watch one of nature's most remarkable ant stories unfold at home.
Print this guide and keep it next to your ant farm. 👉 Keep the essentials close and explore all our free ant care sheets.
