Tetramorium immigrans

Pavement Ant

🐜 At a glance

Origin: 🌍 Europe; it reached North America in the early 1800s, probably in ships’ ballast soil, and is now recorded in 39 US states and three Canadian provinces
Keeping level: Beginner — hardy, fast-growing and active
Queen: 6–8mm, dark brown or black, often with reddish-orange legs
Workers: About 2.75–3.2mm
Founding: Fully claustral — the queen raises her first workers alone
Colony form: Usually a single queen; captive colonies can pass 1,000 workers within a year, wild colonies often 10,000+
Nest temperature: 21–27°C, with a warmer side for the brood
Nest humidity: 40–60% — a lightly moist brood area and a drier retreat
Workers before moving into a nest: 10+
Winter: Hibernation optional — see below

📖 About this species

The pavement ant of North American towns and cities. For decades it was called Tetramorium caespitum, until a 2017 revision split the European complex and matched North American pavement ants to T. immigrans. Hardy, busy and quick to grow, it is one of the easiest ants to raise from a single queen.

📦 When your ants arrive

⚠️ MOST IMPORTANT: leave the parcel completely unopened, exactly as it arrived, at room temperature for 5 hours. The ants must adjust to your home’s temperature gradually — 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 (test tube still in its tin foil and wrapping) in a quiet spot — in daylight, never direct sunlight — away from vibration and daily household activity.
😴 Give the colony 4 to 5 days of complete rest. The ants were fed before dispatch and need nothing from you during this time. Assemble and water the nest while you wait.
Still workers or a motionless queen after delivery are almost always delivery stress. Check the antennae: moving antennae means she is fine. Almost all recover within 4 to 5 days (a little longer for bigger queens).
Do not remove the black divider inside the test tube (between the two cotton stoppers) — it keeps the ants safe in transit. It has a hole, and the queen and all workers pass through it without any issue.
👑 A queen on her own: keep her test tube wrapped in its tin foil and undisturbed. She is fully claustral, so she needs no food until her first workers arrive.

🏠 Moving into the ant farm

Keep the colony in its test tube until it has at least 10 workers. Moved earlier, the workers often abandon the queen in the larger space, which can lead to colony failure.
Connect the test tube to the nest with the delivery tin foil still on and leave it for 14 days. Then slide the foil back about 1mm every day until the tube is fully exposed to daylight.
If the ants have not moved in 2 days after the tube is fully exposed, wrap the foil back on, wait another fortnight and repeat the whole process — patience is the key. Moving in happens on the ants’ own time: anywhere from a couple of days to 6 months.
The red filter and black cover stay on the nest at all times — it is pitch dark inside. The black cover can come off once a day for 2 to 3 minutes (ideally at night); the red filter once a week for 2 to 3 minutes.
☀️ Place the ant farm in normal daylight, never direct sunlight (the sun can overheat a nest within minutes). Avoid windows, radiators and heaters, vibrating surfaces, speakers and TVs, strong smells such as the kitchen, and busy walkways. Keep a steady room temperature.

🍯 Feeding

👑 A founding queen needs no food until her first workers arrive.
🍯 Sugars: a small drop of our organic ant honey or Best Ants UK Ant Nectar — never sugar water.
🥩 Protein: Best Ants UK Protein Jelly, or pre-killed (frozen, then thawed) fruit flies or pieces of mealworm, cricket or roach. Seeds are an optional extra.
Feed 2 to 3 times a week, in the outworld only, in portions smaller than one worker. Remove leftovers within 24 to 48 hours.
🦗 Never feed live insects to a small colony. Use pre-killed prey only: freeze it, thaw it, then serve it in the outworld on a small tin foil tray.

💧 Watering the nest

💧 Use distilled or purified water only — never tap, rainwater or bottled mineral water, even boiled. They carry minerals and microbes that turn a nest green with mould. A litre of distilled water costs a few pounds and lasts over a year.
Water the nest with the pipette provided: pour slowly, a few drops at a time, through the watering hole, and stop as soon as 1 or 2 drops appear inside the nest — that is how you know it is done correctly. More than that is too much.
Once a week is usually right — slightly more in summer, less in winter. Never water the outworld.

🌡️ Temperature and winter

No heating is needed at normal room temperature. If you use a heat mat, warm one side only, never the water end.
Development from egg to worker takes 42 to 63 days at 21–24°C.
❄️ A winter rest is optional: lower the temperature gradually over 2 to 4 weeks to 5–10°C in a cool, stable, unheated space, keep humidity steady, then warm up gradually in spring. Never use a fridge, and never make abrupt temperature changes.

🤩 Did you know?

In spring and early summer, neighbouring colonies fight mass battles on pavements.
Until 2017 these ants were sold and studied under the name Tetramorium caespitum.

⭐ Golden rules | Never break these

🚫 Never put ants in a fridge, and never expose them to abrupt temperature changes. Cold does not kill a colony instantly — the ants get sick and die over the following days — and prolonged cold near freezing damages the sperm a queen stores from her nuptial flight, so she may never lay fertile eggs again.
🚫 Never use gel ant farms, Ytong or concrete nests, or DIY nests.
🚫 Never use tap, rain or mineral water, even boiled.
🚫 Never move a colony into a nest too early, and never tip or shake ants out of their tube.
🚫 Never disturb the colony with tapping or handling — vibration stresses the queen and she can stop laying or eat her eggs.
☀️ Never keep the farm in the dark: ants need daylight for their circadian rhythm. Daylight yes — direct sunlight never.
🚫 Never release this species into the wild. If you can no longer keep it, visit our ants adoption page and ask us whether we can adopt it.

🛒 Recommended for this species

📚 These care notes cover the essentials only. Please read the full ant farm setup guide and our Tetramorium immigrans care guide from A to Z. Questions? Message us through our contact form and we will be happy to help. 💚

Written and reviewed by the Best Ants UK team, keeping ants since 1997.