Acorn Ant Care Guide: How to Keep Temnothorax (Acorn Ants)

Temnothorax are some of the most overlooked ants in the US hobby, and that's a shame. These tiny acorn ants are native across the eastern United States, live in some of the smallest natural nest sites imaginable, and run colonies of only 50 to 200 workers. That tiny scale is exactly what makes them so interesting. If you want to observe ant colony behavior up close, in a setup that fits on a shelf corner, Temnothorax are hard to beat.

They do come with some real challenges. The workers are around 2 to 3 mm long, which means escape prevention and feeding require extra care. Housing needs to match their preference for tight, pre-formed cavities. But for a keeper who is ready to meet those needs, Temnothorax offer a window into ant life that larger species simply cannot provide.

US Range and Habitat

Temnothorax is a large genus with dozens of species in North America. In the eastern US, the two you are most likely to encounter in the hobby are Temnothorax curvispinosus (the orange acorn ant) and Temnothorax longispinosus (the black acorn ant). Both range widely across the eastern half of the country, from the mid-Atlantic states down through the Southeast and into the Midwest.

In the wild these ants nest almost exclusively in pre-existing cavities. Hollow acorns, dead twigs on living trees, small galls, and crevices under bark are all used. They do not excavate their own tunnels the way Camponotus or Formica do. They find a cavity that fits their colony, move in, and defend it. This behavior is central to how you should house them in captivity.

Identifying Your Ants

T. curvispinosus workers are orange-brown to tan, with a noticeably spiny petiole, and run about 2 to 3 mm long. Queens are darker, around 4 to 5 mm. T. longispinosus workers are darker, ranging from brown to nearly black, and are similar in size. Both species have a two-segmented waist and are monomorphic, meaning all workers are roughly the same size with no majors or minors.

If you find a dealate (wingless) queen in an acorn or twig, she is likely already founding a colony. Queens of this genus are very small compared to most species people keep, so do not be surprised when your queen looks almost worker-sized at first glance.

Setting Up a Nano Colony

This is where Temnothorax really shines as a hobby ant. You do not need much space at all, and the setup can be genuinely beautiful in its simplicity.

Housing Options

Because these ants live in pre-formed cavities in nature, the best nest options mimic that exactly. A few approaches work well:

• Natural acorns or hollow twigs: Drill a 1 mm entrance hole into a large acorn or a short section of dead hardwood twig. The ants will move in quickly. This is the most natural option and very effective for small founding colonies.
• Nano formicarium: A small acrylic or resin nest with chambers sized for tiny workers. Look for setups with chamber depths of 2 to 3 mm and entrance holes no larger than 1.5 mm. Any larger and the colony will not feel secure, or will use the space for refuse.
• Test tube setup: Fine for the founding stage. Once the colony reaches 30 to 50 workers, transition them to a proper nano nest.

Keep the outworld small and heavily structured. Temnothorax workers are fast and tiny, and a bare, open outworld stresses them out. Add twigs, cork bark pieces, or small stones to give them terrain to navigate. One keeper tip worth knowing: do not put any thermometers or hygrometers in the outworld. Temnothorax have a habit of treating these as nest sites and moving in.

For a ready-made housing option, check out the Esthetic Ants USA formicarium collection for small and nano setups suited to tiny species.

Temperature and Humidity

Room temperature works for most of the year. Aim for 20 to 24°C in the nest area, and allow the outworld to fluctuate naturally between about 18 and 28°C. Humidity in the nest should be moderate, around 50 to 60%. Mist one side of the outworld every few days with a spray bottle to maintain a slight humidity gradient. The nest itself should not be waterlogged.

Feeding Your Colony

Temnothorax need both protein and carbohydrates, just like any other ant. The catch is the delivery. Workers are so small that a single drop of liquid with normal surface tension can drown them. Keep this in mind with every feeding.

• Sugar: Use diluted honey (1 part honey to 4 parts water) or sugar water, applied in very small drops on a piece of foil or a bottle cap. A toothpick tip of honey placed on a surface they can walk around is safer than a loose pool of liquid.
• Protein: Small pieces of prekilled insects work well. Fruit flies (Drosophila) are ideal, as they are exactly the right size. Pinhead crickets, small mealworm pieces, or pieces of roach nymph all work. Feed protein two to three times per week for a young colony, scaling up as worker count grows.

Remove uneaten protein within 24 to 48 hours to prevent mold. Because the colony is small, they will not eat large amounts, so err on the side of feeding less rather than more. For more detail on ant diet basics, see our complete ant feeding guide.

Fission Reproduction

One of the more unusual things about Temnothorax is that some species reproduce through colony fission rather than the typical nuptial flight and independent founding. In fission, a mature colony splits into two groups, with part of the workforce following a new queen to a nearby nest site. The original colony retains its existing queen and continues.

This means that when your colony matures, you may find it suddenly attempting to move into an adjacent cavity, or you may notice a division of workers seemingly setting up a second nest. This is normal behavior. If you provide two connected nest options, the colony can manage its own population dynamics naturally.

Some species, like T. longispinosus, are also facultatively polydomous, meaning a single colony can spread across multiple nest sites during summer and consolidate in winter. In captivity this plays out as the colony using multiple chambers or cavities if you provide them.

Nuptial flights also occur in this genus. In the eastern US, flights for T. curvispinosus typically happen on warm humid afternoons from June through August. If you are looking to catch a founding queen, check around hardwood trees with abundant leaf litter and dead wood debris during that window.

Hibernation

Temnothorax in the eastern US require a winter dormancy period. Without it, colonies kept at room temperature year-round tend to decline over time. The good news is that these ants are cold-hardy to an impressive degree.

Start cooling your colony gradually in October. An unheated garage, a basement, or the vegetable drawer of a refrigerator all work. Target a temperature between 5 and 10°C. Keep them there from October through February or early March, then bring them back to room temperature gradually. During hibernation they need almost no food or water, though a very occasional mist on the outworld wall is fine.

For a full walkthrough of the hibernation process, see our hibernation guide for US ant keepers.

Common Problems and Solutions

Escape risk: At 2 to 3 mm, Temnothorax workers can slip through gaps that would not concern you with larger ants. Use fluon or another anti-escape barrier on all outworld walls. Check seams on your formicarium carefully. A missing worker is almost impossible to catch.

Mold: Small colonies in humid setups are susceptible to mold, especially when uneaten protein sits too long. Remove food promptly and make sure the nest does not stay permanently wet. Good airflow in the outworld helps.

Colony refusing to move in: If you offer a new nest and the ants ignore it, try covering the setup with a dark cloth for a day or two. Temnothorax prefer darkness when choosing a nest. You can also gently warm the new nest side slightly, which signals a favorable microclimate.

Slow growth: These colonies grow slowly. A founding queen in her first year may produce only 3 to 10 workers. A colony of 100 workers can take two to three years to build up. This is normal. Do not try to accelerate it with extra heat or overfeeding.

Slave-making risk: A small number of Temnothorax species in the eastern US are social parasites that raid other Temnothorax colonies. This is not a concern in captivity as long as you are not housing mixed colonies, but it is worth knowing when collecting in the wild.

Quick Stats