# Red wood ant (Formica rufa) > A large, mound-building European ant that defends colonies with strong bites and formic acid, common in woodland habitats. Source: https://insectscanner.com/species/red-wood-ant/ (updated 2026-10-10) ## Is it dangerous? **Formic acid spray.** Workers do not have a venomous sting but bite with their mandibles and can spray formic acid into the wound or onto skin, causing pain, burning and localized irritation. Reactions are usually mild; rare allergic responses can occur. For bites, wash with soap and water and apply a cold compress. Seek medical help if there are signs of an allergic reaction. **Pets:** Bites and formic acid can irritate pets' skin; small animals could get multiple bites if disturbing a nest. Most pets suffer only temporary discomfort. If a pet shows severe swelling, breathing difficulty or prolonged distress, seek veterinary care. ## Quick facts - Scientific name: Formica rufa - Also called: Southern wood ant, Horse ant - Order: Hymenoptera (Bees, wasps and ants) - Family: Formicidae (Ants) - Size: Workers 4.5-9 mm; queens 8-14 mm - Colours: Reddish brown, Dark brown, Black - Habitat: Coniferous and mixed woodlands, forest edges, heathland and sometimes gardens; nests on sunny, well-drained slopes. - Range: Widespread across Europe and parts of western Asia; not native to the Americas. - Active: Active mainly in spring to early autumn; foraging during daylight, especially warm sunny hours. - Lifespan: Workers 1-3 years; queens commonly 5-15+ years under natural conditions. - Effect on plants: Garden helper - Pest: no ## Overview Formica rufa is a social, mound-building ant native to much of Europe and parts of western Asia. Colonies form conspicuous nests made of soil, twigs and pine needles, often clustered into large ant hills. Workers forage for insect prey and collect honeydew from aphids; they also defend the nest aggressively by biting and spraying formic acid. Colonies are long-lived and can persist for many years, with a single queen or multiple queens in some populations. ## How to identify it Workers are bicolored: reddish-brown head and thorax with a darker brown to black gaster (abdomen). They are relatively large for ants, with robust mandibles and visible segmentation. Nests are dome-shaped mounds, often 30-150 cm across and 20-100 cm high depending on colony age and site, composed of plant material and soil. Winged males and queens appear during reproductive flights in summer. - Bicolored worker ants: reddish-brown head and thorax with a darker gaster. - Large, conspicuous dome-shaped nest mounds made of twigs, needles and soil in sunny forest clearings. - Workers relatively large (4.5-9 mm) with robust mandibles; often seen in trails foraging for prey or aphid honeydew. ## Lookalikes - **Hairy wood ant** (Formica lugubris): Very similar in appearance and ecology, but workers are noticeably hairier (including hairs on the eyes) and the species is mainly found in northern and upland areas; a hand lens is often needed to separate them. - **Formica exsecta (Narrow-headed ant)** (Formica exsecta): F. exsecta is smaller and has a narrower head and differently shaped thorax; nests may be smaller and more scattered. ## Life cycle - **Egg:** Tiny, oval white eggs laid by the queen inside the nest; workers care for and move eggs within the brood chambers. - **Larva:** Wingless, grub-like larvae fed and tended by workers; growth depends on colony food supply. - **Pupa:** Pupae are often enclosed in a silk-like cocoon (varies by species) and are immobile while undergoing metamorphosis. - **Adult:** Workers, males and queens emerge; workers forage and maintain the nest, while queens reproduce. Winged reproductives fly in nuptial flights. ## Diet and predators - Young eat: Fed by workers on regurgitated insect prey, honeydew and protein-rich secretions. - Adults eat: Workers eat insect prey, carcasses, sugary honeydew from aphids and nectar; they commonly tend aphid colonies to harvest honeydew. - Predators of the young: Woodpeckers and other insectivorous birds, beetle predators and parasitic insects. - Predators of adults: Birds, small mammals, spiders and predatory insects; some specialized parasitoid flies and wasps attack brood or adults. ## Effect on plants and gardens Red wood ants prey on herbivorous insects and tend aphids for honeydew. They can reduce some pest insects but may protect aphid populations that feed on trees and shrubs. ## Where and when to find it Look for dome-shaped mounds in sunny clearings, woodland rides, or heathland. Foraging workers travel on visible trails from the nest to aphid-infested trees and shrubs. - Best time: Best seen from late spring through early autumn on warm sunny days, especially mid-morning to mid-afternoon. - Tips: Approach nests slowly and avoid disturbing them. A telephoto or macro lens from a short distance captures worker foraging and nest structure without provoking aggressive defence. ## Fun facts - Red wood ant nests can last for decades and grow larger each year as the colony accumulates material. - They farm aphids like livestock: workers protect aphids from predators and 'milk' them for honeydew. - Colonies can cooperate in groups of nests (polydomy) linked by worker trails to share resources. ## Frequently asked questions ### Do red wood ants bite? Yes. Workers bite with their mandibles and can hold on while spraying formic acid, which causes a burning sensation. ### Are red wood ants dangerous to humans? Only mildly. They have no life-threatening venom, but bites with formic acid can be painful and cause local irritation; allergic reactions are rare but possible. ### Why is a red wood ant nest in my garden? They build nests in sunny, well-drained spots with nearby sources of food like aphids, other insects and plant sap. Gardens adjacent to woodland or with hedges are suitable sites. ### How can I get rid of a red wood ant nest? Avoid destroying large nests; if removal is necessary, contact local pest or conservation authorities because these ants are ecologically important in many areas. For small nuisance nests, professional ant control using targeted baits or nest treatments is most effective and least disruptive. Do not burn nests; this is unsafe and ineffective. ### Will these ants damage my house or plants? They do not eat wood like carpenter ants and generally do not damage buildings. They can protect aphids that harm plants, but they also reduce many herbivorous insects and can be beneficial in gardens. --- More about this species: [iNaturalist](https://www.inaturalist.org/taxa/53853), [Wikipedia](https://en.wikipedia.org/wiki/Formica_rufa). Identify insects and spiders from a photo with the Insect Scanner iPhone app: https://apps.apple.com/app/id1543946563?pt=126685406&ct=web-markdown&mt=8 Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.