Leafcutter ant
Acromyrmex octospinosus
Where it comes from
- Range
- Central America, northern South America and the Caribbean
- Size
- Workers 2–10 mm, queen 15–20 mm
- Queens
- One queen
Keeping them
- Diet
- Fresh leaves and petals to feed their fungus — the fungus feeds them
- Founding
- Claustral, but the queen carries a pellet of fungus and the garden must survive with her
- Brood development
- Egg to worker in roughly 6–8 weeks at 25 °C
- Nest
- A humid fungus chamber plus a foraging arena — condensation must not drip
- Wintering
- No winter rest — keep them warm all year
You are keeping a fungus as much as an ant colony, and the fungus is the fragile half: it dies if the air dries out and rots if water drips on it. You also need pesticide-free leaves every week of the year, which is the part most keepers underestimate.
Starting a colony
A leafcutter queen does not start alone. Before her mating flight she takes a small pellet of fungus from her mother's garden, carried in a pocket in her mouth, and the first thing she does in her new nest is plant it. From then on there are two things to keep alive: the queen and her garden. The garden has to be fed from the start, so a founding queen needs small amounts of fresh leaf or petal material within reach. At 25 °C, egg to worker takes roughly 6–8 weeks.
Founding is where most attempts fail, because a small garden is easily lost. Most keepers start instead with a colony that already has workers and an established garden. That is by far the safer way in.
The fungus garden
The ants do not eat leaves. They cut them, chew them to a pulp and grow a fungus on it, and the fungus feeds the colony. That makes the garden the heart of the setup, and most of its care comes down to the air around it. Keep the fungus chamber at 80–90 % humidity and a steady 24–26 °C, and arrange the setup so condensation runs down the walls rather than dripping from the lid.
A healthy garden is a grey-white, spongy mass with workers all over it. A garden that turns brown, shrinks or is suddenly abandoned is in trouble, often from a parasitic mould called Escovopsis that attacks leafcutter gardens. A strong colony keeps it in check. A weak one may not.
Leaves
The garden needs fresh leaves all year round, and they have to be free of pesticides. Bramble is the staple in Europe because it keeps its leaves through the winter. Rose, oak, hazel and privet leaves and rose petals are taken too, and a colony may prefer one over another. Avoid leaves from roadsides and from plants that have been sprayed, and remember that cut flowers from a shop are often treated. Offer what the colony can process in a day or two and take away what wilts.
The workers carry spent garden material and dead ants to a waste dump, which should be in a separate chamber or a corner of the foraging arena, away from the garden. Empty it regularly. It is where moulds and pests build up.
No winter
This is a tropical American ant, and it needs no hibernation. Warmth, humidity and leaves are needed in every month of the year, and in a northern winter the leaves are the hard part. Know where your bramble will come from in January before you buy a colony.
Common mistakes
- Leaves from sprayed plants, roadsides or a florist.
- Condensation dripping onto the garden.
- Air that is too dry for the fungus.
- No plan for leaves in winter.
- Leaving the waste dump to grow.
Questions keepers ask
Why are some workers white? That white crust is bacteria. Acromyrmex workers carry them on their body, and the bacteria make substances that help keep the garden parasite Escovopsis in check. It is a sign of a working colony, not of disease.
What do I feed in winter? Bramble, mostly. It stays green through a European winter and the ants take it readily. Some keepers grow a supply of bramble or rose in pots so they never run short.
Can the colony live on the fungus alone? Only as long as the fungus is fed. Without fresh leaves the garden shrinks, and the colony with it.
Is it for beginners? No. It is the most demanding species in the guide, because the garden needs as much looking after as the ants. Get some experience with an easier species first, such as Camponotus nicobarensis, which also needs no winter.
Check it yourself
General guidance from the usual beginner references — treat it as a starting point, not as a rule your colony has agreed to.
Start a colony with this species
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