Formica rufa (red wood ant)

Introduction to Formica Rufa

With their large mounds the red wood ants can claim gigantic territories. This ant species is famous for their aggressive behavior and that they happily shoot formic acid at its enemies. The population of Formica rufa colonies can reach well beyond 100.000 workers.
Formica Rufa red wood ant worker
A Formica Rufa worker sporting its classic red and black color. Photo: Richard Bartz, Munich Makro Freak CC BY-SA 2.5

The appearance of Formica Rufa

Worker: Length 2-4,5 mm. Color varies from brown-yellow to bright yellow. Legs and body are relatively hairy with hairs aligning with the shape of the body. The head is more sparsely haired with tiny eyes. The hairs are long and stand up on the top of the abdomen and middle body segment (this separates the species from the very much alike species of Lasius bicornis. The species do not have these hairs on the first part of the abdomen, postpetiole). The upper part of the middle segment is wider than the lower parts. They have a small scent of citrus which can be picked up by humans. The rare Lasius carniolicus is one of the Lasius species with the strongest citrus scent. Workers of Lasius flavus can vary in size depending on climate. In the northern parts of their distribution area (for example Scandinavia) the workers have a much more diverse size difference in-between one another. In the southern parts the size of the flavus workers are more the same.

Queen: Length 7-9 mm. In comparison with the worker yellow of her daughters, the queen is more brown (varies between light and dark brown, but her underbody is always lighter). Same hairs as the workers. The head is clearly thinner than the rest of the forepart of the body. The eyes are haired with many short hairs.

Males: Length 3-4 mm. Darker than the queen, more a black and brown or dark brown color. Lacks hairs on the long inner segment of the antennas. Just as the queen the head is thinner than the forepart of the body.


Formica Rufa is found throughout Europe with the exception of the most southern parts. The distribution of the red wood ant is wide. From the middle parts of the Northern European area all the way east to Mongolia.

Nuptial flights

The nuptial flights of Formica rufa happens from the middle of May to the beginning of July. The flying ants most often go outside early in the day or in the beginning of the afternoon. The mating is handled on top of the ant hills or in classic flying manner. (6) New colonies are not established by a single brood bearing queen (claustral), but instead they conduct nest founding through parasitism. The newly mated queens aim to take over an already functioning nest of another ant species (in most European cases the species of Formica fusca or Formica lemani). What sets the red wood ant queen apart from other parasitic ant queens is that she does not employ advanced strategies such as playing dead or using smell to confuse the workers. Instead she simply make a run for it, head first straight into the colony. Like a sprinter she bets her life on being able to get inside and take over as queen before the workers kill her. In most cases she does not survive. But the success of the Formica rufas throughout Europe suggests that many queens are in fact not running in vain. (7)

A very classic Formica Rufa nest situated in the middle parts of Sweden. Photo © Antkeepers

Formica rufa habitat and nests

Formica rufa is the center species of the mound building family of wood ants (the family is actually called Formica rufas and consist of a total of five species). They build enormous ant hills in coniferous as well as deciduous forests. This means that they settle by both the pine needles as well as the leave bearing trees. But they seem to like the pines more than anything else. Their mounds are often the shape of domes but they can also be more of a flat build when the ants settle out in the open. Some species of the Formica family sometimes even build inverted domes, with a dip in the middle. (2) This is probably a way of taking better advantage of weather and surroundings. Read more about ant hills here.


These numbers are unfortunately not confirmed by researchers. The lifespan of Formica rufa is reported throughout the internet, but should be taken more as an estimation from enthusiasts: Lifespan of the queens: 10 years. Lifespan of the workers: 1-3 years.

Formica rufa – from egg to ant

5-6 weeks. (9) What can be said about the brood process of Formica rufa is that their larvae spin yellowish cocoons when they pupate. Often mistaken for ant eggs. The real ant eggs are of course much smaller, whiter and more transparent.


The Formica rufa family has an interesting caste system that’s been observed in Formica polyctena. The workers are divided into three groups. 1: The Arboreal ants who gathers honeydew from their livestock (aphids) up in the plants of their territory. They can sometimes hunt for prey but primarily tend to gather honeydew. 2: Ground searching workers hunting for prey and food on ground level. 3: Ground searching workers foraging for building material for the ant hill. The workers can freely move in-between these groups but tend to, by observation, stick to one role for at least two weeks before switching. Research shows that workers have different work ethics. Some are very varied and helpful in a great variety of tasks, while others are more focused and passionate about their current group belonging. (8) Read more about castes here: Ants | Caste Systems in Ant Societies


The red wood ant seldom settle their colonies near each other. The ant hills are sparsely placed and often far away from other nests. Some sources claim than the Formica rufas have one or a few queens whilst others claim they can have hundreds of them. Most likely is that the species in general have a more monogyne setup with most having only one queen. (3) The workers are easily spotted outside of the nest since they tend to quickly move around their territory. Their ant roads can reach up to a hundred meters from the nest and are used to gather food and supplies. Formica rufa tend to keep aphids as livestock. They protect them and their host plant in exchange for the sweet honeydew that they emit when touched. There are reports of a Formica colony carrying as much as 500 kg of honeydew back to the colony in a year. (4)


It’s not easy getting your hands on a colony of Formica rufas. Most ant shops do not sell the species and the reason for this is a bit unclear. It’s also a species that’s not super easy to go out and capture since they have enormous nests. What makes it even more difficult is the way they found colonies. One simply can not go out and catch a new queen as easily as with many other ant species.

Something that is important to bear in mind if you keep Formica rufa is that they need a big formicarium. Otherwise, when the colony grows and they get stressed they might kill themselves by filling the air in the formicarium with formic acid. And that’s no fun!

Formica Rufa information:

Phylum: Arthopoda

Subphylum: Hexapoda

Order: Hymenoptera

Superfamily: Vespoidea

Family: Formicidae

Subfamily: Formicinae

Tribus: Formicini

Genus: Formica

Naming: Formica rufa (Linnaeus, 1761)

Pronounciation: [Formíka rúfa]

Etymology: Formica (lat.) = ant, Rufus (lat.) = shade of red

Common name: Red wood ant, Southern wood ant, Horse ant


1. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln ”Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 162, 164, 183-184

2. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln ”Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 164

3. Comparison between Nationalnyckeln p. 184, AntWiki | Formica rufa and The Ants p. 450

4. Bert Holldobler & Edward O. Wilson (1990) ”The Ants” p. 524

5.  Formic acid – Wikipedia

6. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln ”Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 183

7. Bert Holldobler & Edward O. Wilson (1990) ”The Ants” p. 450

8. Bert Holldobler & Edward O. Wilson (1990) ”The Ants” p. 341

9. Bert Holldobler & Edward O. Wilson (1990) ”The Ants” p. 174

Further reading