How to Care for Pheidole morrisii | The Morris's Big-Headed Ant Guide
Photo: Connor Cashman, via iNaturalist, licensed under CC BY 4.0.
Pheidole morrisii is a golden-yellow big-headed ant from the sandy pine barrens, fields and grasslands of the eastern USA. Tiny minors forage and nurse, and big-headed majors help to defend the colony and carry food home.
It is one of the fastest-growing big-headed ants, and a well-fed colony can reach thousands of workers. This guide explains Pheidole morrisii care step by step, from a queen in a test tube to a thriving colony.
Pheidole morrisii is a North American ant, and Best Ants UK does not sell it. North American ants may be illegal or impossible to import into the UK, and we never encourage importing ants. This guide is for keepers where it is native, and for anyone curious.
We have kept ants since 1997, and these are the care rules we use for our own big-headed ants.
👉 In a hurry? Download our free Pheidole morrisii care sheet (PDF) or open the Pheidole morrisii care sheet page for the key facts at a glance.
Pheidole morrisii at a Glance
Also known as: Morris's big-headed ant
Origin: eastern USA, from Long Island in New York south to Florida and west to Texas
Sold by Best Ants UK: no, it is a North American species
Keeping level: Intermediate
Queen: 8 to 10mm, yellow to orange
Minor workers: about 3 to 3.5mm, yellow
Majors (soldiers): 4 to 5mm, yellow, with a big head
Colony: usually one queen (several in some northern populations), 5,000 to 10,000 ants when mature
Nest temperature: 24 to 28°C, best at around 26°C
Nest humidity: 50 to 70%
Workers before moving into a nest: 50+
Winter: a natural winter rest in northern colonies, never a fridge
Escape risk: high, so a PTFE barrier is a must
Meet Morris's Big-Headed Ant
In the wild, Pheidole morrisii loves dry, sandy soil: pine barrens, old fields and grassland. Its nest entrance is often a little crater of soil or sits at the base of a grass clump, with shafts running down to chambers deep underground.
A colony has two kinds of worker. The minors are the tiny all-rounders: they forage, clean and look after the eggs, larvae and pupae (the brood). The majors, with their big heads, defend the colony and help to cut up and carry large finds.
Morrisii is mainly a scavenger. Minors often forage alone at night and bring back dead insects and other scraps.
Its life story changes across its range. In the south, a colony usually has one queen and may spread over several nests. In the north-east, several queens can start a colony together and stay together, which is rare among ants.
Winged queens appear from early summer: in May in Florida and in July further north.
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.
Put it somewhere quiet and still, away from daily household activity. Normal daylight is fine, but never direct sunlight.
Give the colony 4 to 5 days of complete rest, with no food. A good supplier feeds the ants before dispatch. Use this time to set up and water the nest. 👉 Our step-by-step ant farm setup guide shows you exactly 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
Big-headed ants need far more workers than most species before they move into an ant farm. The minors are only about 3mm long, so even a whole young colony takes up very little space. Keep it in its test tube until it has at least 50 workers.
Moved too early, a small colony is lost in the bigger space: the workers abandon the queen and the colony dies. The same 50+ rule applies to a queen on her own.
A queen on her own 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 the queen and colony do far better afterwards. Keep her tube wrapped in its foil and disturb her as little as possible.
With warmth and protein the colony grows quickly. Brood takes about 4 to 5 weeks from egg to worker in a heated setup, and the first majors usually appear in the second or third batch of workers.
Moving Into the Ant Farm
When the colony is big enough, 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. Bit by bit, the tube becomes the bright spot and the dark nest becomes the safe home.
If the ants haven't moved 2 days after the tube is fully exposed, wrap the foil back on, wait another fortnight and repeat. Moving in happens on the ants' own time: anywhere 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. Ants sometimes leave a little 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 Pheidole morrisii
Tiny Pheidole workers squeeze through the smallest gaps, so their home must be well made and escape-proof. A young colony also feels safest in a small nest it can fill.
For every Pheidole we recommend the A7 Plus ant farm kit only (you will find the link at the end of this guide). Its small nest suits tiny workers, and its pre-installed digital meter shows nest temperature and humidity at a glance.
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, and rooms with strong smells such as the kitchen.
Temperature and Heating
Warmth is the secret to a fast-growing morrisii colony. Keep the nest at 24 to 28°C. The brood develops best at around 26°C, and kept too cool it barely grows.
Most UK homes are cooler than that for much of the year. 👉 The Advanced Heating System Small 4W holds a steady warm spot with its digital thermostat. Set it to 26°C, in the middle of the range.
The heat mat goes under one quarter of the nest only, on the side opposite the watering area. The ants can then pick the spot they like best. 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. A watering test tube in the outworld gives the workers a safe drink.
Keep the outworld clean. Morrisii colonies eat a lot of protein, and old scraps in a warm setup quickly grow mould and attract mites.
Feeding Your Big-Headed Ants
A growing morrisii colony is hungry, especially for protein, and protein is what drives its fast growth. Feed twice a week, in small amounts, in the outworld only. Remove leftovers after 2 days to stop mould.
🍯 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. Offer small drops, as tiny workers can get stuck in a big one.
🥩 For the queen and brood, give 👉 Protein Jelly or 👉 Cricket Mash. Keep protein jelly in the fridge at all times.
Serve food on a small piece of tin foil or in a 👉 small feeding dish, so leftovers are easy to lift out.
🌾 Wild colonies gather some seeds, but keepers report that captive colonies rarely take them. If you try a few small seeds, put them on tin foil, never straight on the substrate, where they can sprout.
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 only, and serve it in the outworld. Never chop it smaller, and skip mealworms. The majors drag small pieces into the nest, the tiny workers can't carry the remains back out, and mould follows.
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 and off-licences, dried mealworms, and live food from pet shops or online, where about half carries mites.
Dried mealworms are also useless as ant food. Buy ant food only from established, reputable ant-keeping suppliers. At Best Ants UK we clean our foods before dispatch, freeze our seeds below -60°C in a special freezer, and check every colony twice a month.
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
Morrisii minors are tiny and quick, 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; roll it gently instead.
Winter Care
Pheidole morrisii lives everywhere from New York to Florida, so its winter needs depend on where the colony comes from. Northern colonies have a natural winter rest.
A cool rest at a steady 10 to 15°C for 2 to 3 months suits northern colonies, but only in a specialised hibernation unit with precise temperature control. Without one, keep the colony at room temperature. It slows down anyway, because its biological clock can't be tricked.
We never rest queens in their first year. Never put ants in a fridge, shed or garage, and avoid any abrupt temperature change.
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 a cool hibernation rest, give fresh water only and no food.
Can I Release My Ants?
No. A colony raised indoors won't survive outside, and a North American ant 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 Pheidole morrisii good for beginners?
It is an intermediate species. The colony is hardy and grows fast, but the workers are tiny, it needs steady warmth and a PTFE barrier is a must. For a very first colony, Lasius niger or Messor barbarus is easier.
Can I buy Pheidole morrisii in the UK?
Best Ants UK does not sell Pheidole morrisii. It is a North American ant, and it may be illegal or impossible to import into the UK. We never encourage importing ants.
How many workers does Pheidole morrisii need before moving into a nest?
At least 50 workers. The minors are only about 3mm long, so a smaller colony is lost in an ant farm and can die. Keep it in the test tube until it reaches 50. The same rule applies to a queen on her own.
What temperature do Pheidole morrisii need?
Keep the nest at 24 to 28°C, best at around 26°C. Most UK homes are cooler, so use an Advanced Heating System set to 26°C under one quarter of the nest.
Do Pheidole morrisii hibernate?
Colonies from the north of its range have a natural winter rest. A cool rest at about 10 to 15°C is only safe in a specialised hibernation unit. Otherwise keep them at room temperature. We never rest queens in their first year.
Do Pheidole morrisii eat seeds?
Wild colonies collect some seeds, but keepers report that captive colonies rarely take them. Focus on honey or Ant Nectar and Protein Jelly or Cricket Mash, twice a week in the outworld.
How big does a Pheidole morrisii colony get?
Big. A healthy colony reaches a few hundred workers in its first year, and mature colonies often have 5,000 to 10,000 ants or more.
Ready to Start Your Own Big-Headed Ant Colony?
👉 Start with the A7 Plus ant farm kit. Its small nest suits tiny workers, its pre-installed digital meter shows temperature and humidity at a glance, and if you already have your ants, choose its Nest + Outworld option. 👉 Explore all our free ant care sheets.
