Harvester ant

Messor barbarus

Where it comes from

Range

The Iberian Peninsula, southern France and North Africa

Size

Workers 3–14 mm, queen 14–18 mm

Queens

One queen

Keeping them

Diet

Seeds, with insects for the brood

Founding

Fully claustral — the queen needs no food until her first workers

Brood development

Egg to worker in roughly 5–7 weeks at 26 °C

Nest

Dry nest, dry outworld, and a separate dry chamber for the seed store

Wintering

10–15 °C, a short and mild rest

Seed eaters that mill grain into bread in a dedicated chamber. Keep the seed store dry — damp seed moulds fast and takes the colony with it.

Starting a colony

Messor barbarus queens are big, 14–18 mm, and in their home range they fly mostly in autumn, after the first rains of the season. A queen that has shed her wings has mated and is looking for a place to dig in.

House her in a test tube: water at the back behind a plug of cotton wool, the queen in the dry front half, and a loose plug at the opening. She is fully claustral and lives on her own reserves until her first workers arrive. Keep the tube at 24–28 °C, warming one end rather than the whole tube, and leave her alone. At 26 °C, egg to worker takes roughly 5–7 weeks. The first workers are small. The large-headed majors this species is known for only appear once the colony has grown.

Seeds

This is a harvester ant, and seeds are its main food. The workers carry them into a dry storage chamber, the majors crack them open with their large heads, and the colony chews the kernels into a paste, often called ant bread, that feeds the larvae. Watching that happen is much of the appeal of keeping Messor.

Offer a mix of small seeds: grass seed, chia, poppy, millet, canary seed, flax and crushed sunflower kernels all work, and a bird-seed mix without additives is a good base. Avoid seed sold for sowing, which is often coated with fungicide. The husks are carried out again and piled up in a corner of the outworld. That refuse pile is harmless while it is dry, but take it out now and then, together with any insect remains.

Seeds alone are not enough for a growing colony. Give insects too — fruit flies, crickets, cut mealworms — especially when there is a lot of brood. Some colonies take sugar water and many ignore it. It is fine to offer, but not needed.

The nest

Keep it dry: a dry nest, a dry outworld and a dry place to keep the seeds, with water from a test tube or a small damp corner so the ants can drink. Seed that gets damp does not stay food for long. Messor likes to dig, so sand-and-loam nests suit it well, but Ytong and acrylic work too. Expect the workers to fill gaps and corners with soil and debris.

Most homes are cooler than this species wants, so plan on a heat mat or heat cable under one end of the nest. A colony can reach tens of thousands of workers within a few years, so think ahead about how you will add space.

Hibernation

Messor barbarus takes a short, mild rest: December and January at 10–15 °C, in a cool room or an unheated hallway. A fridge is too cold. The colony slows down but does not stop completely, and workers may still come out for seeds, so leave some seed available and stop offering insects. Keep the water topped up and warm them up again gradually.

Common mistakes

• Damp seeds, or a seed store next to the water.
• Seed treated with fungicide or pesticide.
• Seeds only, with no insects for a growing colony.
• Wintering it like a northern species, in a fridge or a cold cellar.
• Leaving insect remains on the refuse pile.

Questions keepers ask

Which seeds should I give? Small, untreated seeds of different kinds. A plain bird-seed mix, topped up with grass seed, chia and poppy, covers most of what a colony will take. Watch which seeds are carried in and which are left, and adjust.

How long until the first workers? About 5–7 weeks at 26 °C, and longer at room temperature.

Does it need a heat mat? Usually, yes. Put it under one end of the nest only, so the colony has a warm side and a cool side.

How is it different from Messor structor? Messor barbarus is bigger, with more striking majors, and it wants more warmth. Messor structor is smaller, hardier and happier in a cooler room.

Check it yourself

• AntWiki: Messor barbarus

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

Similar species

• Messor structor European harvester ant

  Southern and central Europe eastwards into central Asia

  24–28 °C 40–60 %

  Beginner
• Aphaenogaster senilis Iberian funnel ant

  The Iberian Peninsula and North Africa

  22–27 °C 40–60 %

  Intermediate
• Camponotus barbaricus Mediterranean carpenter ant

  The Iberian Peninsula and North Africa, in dry open country

  24–28 °C 50–70 %

  Intermediate
• Crematogaster scutellaris Acrobat ant

  The Mediterranean basin, in dead wood and cork bark

  24–28 °C 50–70 %

  Intermediate

All 21 species in the guide