How to Care for Pogonomyrmex californicus | The California Harvester Ant Guide for Adult Keepers
Pogonomyrmex californicus, the California harvester ant, is a fiery red desert ant that gathers seeds across the hot, sandy south-west of North America.
It is one of the few harvesters where some colonies are run by several queens working together. This guide explains Pogonomyrmex californicus care step by step, for careful adult keepers, because this ant has a serious sting.
We have kept ants since 1997, and the care rules here are the ones we use every day with our own harvester ants.
👉 In a hurry? Download our free Pogonomyrmex californicus care sheet (PDF) or open the Pogonomyrmex californicus care sheet page for the key facts at a glance.
Pogonomyrmex californicus at a Glance
Origin: the south-western United States (California, Arizona, Nevada, Utah, New Mexico and Texas) and northern Mexico
Keeping level: Advanced, for adults only (very painful sting)
Queen: about 9 to 12mm
Workers: about 5.5 to 8.7mm, all one size, rusty red, sometimes with a darker gaster
Colony: usually one queen, sometimes several; a few thousand workers when mature
Main food: seeds
Nest temperature: 24 to 28°C
Nest humidity: 50 to 60%
Workers before moving into a nest: 10 minimum, 15 to 20 recommended
Winter: a 2 to 3 month rest at about 17 to 18°C, never below 15°C
Water: never open water, a watering test tube only
Sold by Best Ants UK: no, it is a North American species
Meet the California Harvester Ant
In the wild, Pogonomyrmex californicus lives in almost every dry habitat of its range, from weedy slopes to grassland and creosote scrub. It prefers sandy soil, with a small mound and a single entrance inside a crater of loose, sandy soil.
Below the surface, the tunnels can run down about 2 metres, with chambers for seeds and brood. A mature colony averages a few thousand workers, and each nest can send out winged queens and males on several flights from May to July.
The workers forage by day but take cover in the hottest hours. On scorching ground they run stiff-legged with the gaster raised, or climb onto pebbles to cool down. At night and in the midday heat, they often close the nest entrance with soil or pebbles.
Most colonies have one queen. In some populations, though, several young queens dig a nest together and carry on living side by side, which makes this species a favourite of scientists who study ant teamwork.
Can You Keep Pogonomyrmex californicus in the UK?
Pogonomyrmex californicus is a North American ant, and Best Ants UK does not sell it. It may be illegal or impossible to bring into the UK, so please never try to import it, and never buy it from anyone offering to ship it here.
This guide is for keepers who live where the species is native and can keep it legally, and for anyone curious about harvester ants.
If you are in the UK and dream of harvesters, our Messor barbarus is a calm, hardy harvester ant with no sting at all, and much of this guide works for it too.
Watch our Messor barbarus care guide, filmed with our own 19-year-old harvester ant colony:
A Painful Sting | Adults Only
This harvester has one of the most painful ant stings in its region. The barbed sting can tear off and stay in the skin, like a honeybee's, and the pain can last for hours. In some people a sting can cause an allergic reaction: get medical help straight away if that happens.
Keep this species for adults only, out of reach of children and pets. Never handle the ants, never put your fingers into the outworld, and use long tweezers for any work inside it.
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. Daylight is fine, never direct sunlight.
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, and big harvester queens can take a little longer.
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. The same rule applies to a queen on her own.
A founding queen still needs a little 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 fed queen raises her first workers faster and does 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. Take colony photos once a month at most.
The Best Ant Farm for Pogonomyrmex californicus
👉 For harvester ants we recommend the Angie ant farm starter kit, our harvester ant farm with a pre-installed digital meter. It shows the nest temperature and humidity at a glance, which matters a lot here, as too much water makes seeds sprout.
The A7 Plus ant farm, also with a pre-installed digital meter, is a great choice too. If you already have your ants, choose its Nest + Outworld option.
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 24 to 28°C. Most UK homes are cooler than that for most of the year, so this species cannot thrive without gentle heating.
👉 We recommend the Advanced Heating System Small 4W. Its digital thermostat holds a steady warm spot. Set it to 26°C, the middle of the ideal range.
On a horizontal nest such as Angie or the A7 Plus, the heat mat goes under one quarter of the nest. On a vertical nest, it goes under half. Always put it on the side opposite the watering area, so the ants can choose their spot.
The outworld can cool to about 18°C overnight and warm 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.
Water and Humidity
Keep the nest humidity at 50 to 60%. This is a dry-country ant, and too much water makes stored seeds sprout and mould. Use distilled or purified water only. Never use tap water, rainwater or bottled mineral water, even boiled.
Water the nest about once a week with the pipette provided. Pour very slowly, a drop at a time, through the watering hole. With harvesters, be extra careful: no more than 1 drop should leak into the nest.
With a meter, simply water when the nest humidity drops below 50%, a little sooner in summer and later in winter.
Never water the outworld. Keep it dry, at about 50% humidity, like an average UK home.
Harvester ants must never have open water, because they can drown in it. Give them a watering test tube in the outworld, not a water dispenser. Much of the water they need comes from their food.
Feeding Your Harvester Ants
🌾 Seeds are the main food. Give our 👉 harvester ant seed mix. Start with a small pinch and give more as the colony grows and collects it.
Always put the seeds on a piece of tin foil or in a 👉 small feeding dish in the outworld. Never put them straight on the substrate: damp seeds sprout, and sprouted seeds are harmful to the colony.
🥩 Once a week, for example every Monday, give a little 👉 Protein Jelly. The queen and brood need it to grow. Keep protein jelly in the fridge at all times.
🍯 Once a week on another day, for example every Thursday, 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.
Young colonies and lone queens lean more on protein and honey than on seeds. Feed in the outworld only, and remove leftover jelly and honey after 2 days to stop mould.
Keep Mites Out of Your Colony
Blood-sucking mites are one of the biggest dangers for harvester ants, and they are not rare. They often arrive with bird seed from local shops and off-licences, dried mealworms (useless as ant food), and live food from pet shops or online, where about half 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.
A home freezer won't kill all the mites in seeds, so never rely on it. We freeze our seeds below -60°C in a special freezer before they reach you.
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
With a stinging species, escape-proofing matters even more. 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 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; roll it gently instead.
Winter Care
In the wild, Pogonomyrmex californicus slows down in winter. In captivity, give it a winter rest of 2 to 3 months, for example from December to February, at about 17 to 18°C. It does not need a cold hibernation.
Harvesters are sensitive to cold: 15°C is the absolute minimum, and 17°C or above is safe. Switch the heating off for the rest and let the room cool gradually. Never put ants in a fridge, shed or garage, and never move them from a warm room straight into a cold one.
If the room drops below 17°C, set the heater's thermostat to 17°C: it switches on at 16°C and off again at 17°C. We never give a queen a winter rest in her first year: keep her at her normal warmth.
The colony slows down in winter anyway, because its biological clock can't be tricked. Feed less, but never guess. At 17 to 22°C, give about a third of the summer amount. At 22 to 26°C, give about half.
Can I Release My Harvester Ants?
No. A colony raised indoors won't survive outside, and this species doesn't belong in the wild here. If you ever 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 Pogonomyrmex californicus good for beginners?
No. It is an advanced species for adult keepers only, because it has a very painful sting. For a first harvester colony in the UK, Messor barbarus is far easier and has no sting.
Can I buy Pogonomyrmex californicus in the UK?
No. Pogonomyrmex californicus is a North American ant and Best Ants UK does not sell it. It may be illegal or impossible to bring into the UK, so please never try to import it.
What do Pogonomyrmex californicus eat?
Seeds are their main food, from a harvester seed mix bought from an established ant-keeping supplier. Add Protein Jelly once a week and organic honey or Ant Nectar once a week on another day. Always feed in the outworld only.
What temperature do Pogonomyrmex californicus need?
Keep the nest at 24 to 28°C. Most UK homes are cooler than that, so use the Advanced Heating System Small set to 26°C under one quarter of a horizontal nest, opposite the watering area.
Do Pogonomyrmex californicus hibernate?
They need a winter rest of 2 to 3 months at about 17 to 18°C, not a cold hibernation. Never let them drop below 15°C. A queen in her first year stays warm through her first winter.
Can a Pogonomyrmex californicus colony have more than one queen?
Yes, in some populations. Most colonies have a single queen, but in parts of California and Arizona several queens found a colony together and stay together. Never put queens from different places together yourself.
Do Pogonomyrmex californicus sting?
Yes, and it is very painful. The barbed sting can stay in the skin, and in some people a sting can cause an allergic reaction. Keep this species for adults only, never handle the ants, and keep the outworld lid closed.
Start Your Own Harvester Ant Colony
Print this guide and keep it next to your ant farm. In the UK, the easiest way to enjoy harvester ants is a colony of Messor barbarus, with no sting to worry about.
👉 Ready to start? Our A7 Plus ant farm kit has a pre-installed digital meter and a Nest + Outworld option, and it makes a superb home for harvester ants. 👉 Explore all our free ant care sheets.
