Guide to the Wood Ants of the UK and related species © Stewart Taylor © Stewart Taylor Wood Ants of the UK This guide is aimed at anyone who wants to learn more about mound-building woodland ants in the UK and how to identify the three ‘true’ Wood Ant species: Southern Red Wood Ant, Scottish Wood Ant and Hairy Wood Ant. The Blood-red Ant and Narrow-headed Ant (which overlap with the Wood Ants in their appearance, habitat and range) are also included here. The Shining Guest Ant is dependent on Wood Ants for survival so is included in this guide to raise awareness of this tiny and overlooked species. A further related species, Formica pratensis is not included in this guide. It has been considered extinct on mainland Britain since 2005 and is now only found on Jersey and Guernsey in the British Isles. Funding by CLIF, National Parks Protectors Published by the Cairngorms National Park Authority © CNPA 2021. All rights reserved. Contents What are Wood Ants? 02 Why are they important? 04 The Wood Ant calendar 05 Colony establishment and life cycle 06 Scottish Wood Ant 08 Hairy Wood Ant 09 Southern Red Wood Ant 10 Blood-red Ant 11 Narrow-headed Ant 12 Shining Guest Ant 13 Comparison between Shining Guest Ant and Slender Ant 14 Where to find Wood Ants 15 Nest mounds 18 Species distributions 19 Managing habitat for wood ants 22 Survey techniques and monitoring 25 Recording Wood Ants 26 Conservation status of Wood Ants 27 Further information 28 01 What are Wood Ants? Wood Ants are large, red and brown-black ants and in Europe most species live in woodland habitats. They are known around the world as thatch or mound ants due to the mounded nests they build. There are 13 described species of these ants in Eurasia and 19 species in North America. Like all ants they are social and cooperate to look after the brood, care for the nest and source food. Biology and ecology Wood Ants build large thatched dried grass and even pieces of lichen. mounds in which to live and The thatch acts like a solar panel aggressively defend both their nest to raise the temperature of the and food resources. As their name nest above that of its surroundings suggests, they are associated with (a high temperature is crucial for woodland; coniferous forest, mixed brood development). The thatch and broadleaf woodland with well also acts as an umbrella so that rain drained soils being favoured. Nests water trickles away from the nest, are usually south or south-east facing keeping it dry. to maximise the amount of sunlight warming the nest. All species of ants in the UK hibernate over the winter. In Nest mounds vary tremendously mound-building ants, they retreat in size and shape, ranging from fist- to the underground parts of their sized to 2m tall. What you see above nests where the temperature is ground is at least mirrored (and stable and free of frost. The best sometimes exceeded) underground. time to look for active nests is Internally the nest contains a series from spring to autumn. Ants of tunnels and chambers containing emerge from hibernation once the queen, a nursery for the brood temperatures are consistently and food stores. Tunnel entrances above freezing and ‘swarm’ on the can be opened or closed to maintain surface of the nest in sunny weather optimal temperature and humidity. to warm themselves (and boost the temperature of the nest). The On the surface, the ‘thatch’ is made movement of the ants swarming of organic materials such as pine on the nest surface in spring needles, small twigs, moss, heather, actually makes an audible sound. 02 Swarming behaviour of Wood Ant workers on the nest surface in spring. Queens rise to the surface at this time and can be identified by their larger size in relation to the workers and their large glossy abdomens. © Jenni Stockan © Jenni Diet Wood Ants are omnivorous and prey on a wide range of other invertebrates. Caterpillars, aphids, spiders, beetles and many others (including other ants) are taken, their diet changing to suit local abundances of different prey. Workers subdue their prey by biting and spraying formic acid. A small proportion of © J.M.S.Robinson their diet includes seeds, tree sap and berry juices. They will also scavenge A Southern Wood Ant on dead invertebrates. (Formica rufa) worker guarding a collection of aphids. Between 60% and 90% of the diet of the workers comes from honeydew produced by aphids feeding on the sap of trees and shrubs. This sap is high in sugars and as the aphids feed they excrete excess sugars as honeydew. Ants ‘milk’ the aphids of Ants ‘milk’ the aphids of their honeydew, and in return protect their honeydew, and in the aphids from predators and even “ ” return protect the aphids move them to better feeding grounds. The Blood-red Ant is predominantly from predators and even predatory on other ants but will move them to better also feed on seeds, berries and take feeding grounds. honeydew from aphids. 03 Why are they important? Not only are Wood Ants fascinating and beautiful insects in their own right, but they perform a number of important roles in the forest ecosystem, earning them the status of “ecosystem engineers”. Wood Ants: The Wood Ant’s nest is home to a unique community of specialist • Affect tree growth through their invertebrates. This includes the relationship with aphids in the Shining Guest Ant but also specially tree canopy and through removal adapted beetles, moths and even of insect herbivores (e.g. moth woodlice which live inside ant caterpillars) mounds and nowhere else. There • Accumulate huge amounts of is also a concentration of micro- organic material and minerals in organisms within Wood Ant nests their nests, particularly nitrogen which breakdown unwanted food and phosphorus (the nests not and nest materials. only increase the amount of mineral nutrients but also make them more available to plants) • Help distribute the seeds of plants, including some plant species which have sugary coatings on their seeds to make them attractive to ants • Are used by a range of bird species to remove parasites (behaviour known as ‘anting’ – birds aggregate the surface of the nest, causing the ants to © Wiswell Hayley spray formic acid onto the bird’s feathers which kills parasites) Larva of the beetle Clytra quadripunctata with its case In addition Wood Ants are a food made of plant material. The source for vertebrates such as larvae wander about on the Capercaillie, Badger and Pine Marten surface of Wood Ant nests to name a few. Some species feeding on plant debris and specialise in feeding on Wood Ants, use their case as protection such as the Green Woodpecker from the Wood Ant workers. and the Gallows Spider. 04 The Wood Ant calendar This is generalised across the species in this guide and timing of events will vary between species and parts of the UK, nest altitude, local climate etc. November – February/March June – September Hibernation Raising worker offspring March – April May – June Spring swarming (Wood Ants only, Raising queens and males timing dependent on ambient (from eggs laid in late winter/ temperature and levels of sunshine). early spring). In southern UK, Wood Ants can emerge as early as February, depending on weather. Activity of the workers begins when the internal nest temperature rises to between 25-30°C. May – October June – August General worker activity – foraging, Emergence of virgin queens and aphid farming, repairing and building males, mating flights take place. nest. Number of active workers This is usually confined to a involved in foraging peaks in mid- relatively short window of 2-3 summer. Size of individual workers weeks. In southern England can varies greatly within the colony be as early as May, in northern and depends on the quality of diet Scotland may be as late as during the larval stage. July-August 05 Colony establishment and life cycle 1 Mating Queens and males undertake mating flights. Queens drop their wings soon after mating. 2 Colony establishment Social parasitism Mated queen Nest budding Establishes a new colony returns to natal nest takes place by parasitising the nest of When there are a different ant species multiple queens in a single nest 3 Lifecycle of an ant Queen Queen lays eggs Male Hatch into larvae Pupate when fully Worker developed – pupae can be cocooned or ‘naked’. 06 1.1 Mating Wood Ants and Narrow-headed Ants can Colony establishment and life cycle exist in ‘super colonies’ which comprise Newly emerged queens and males take of multiple mounds (known as polydomy, to the wing. Males usually emerge first which means ‘many homes’). Workers and disperse to reduce chances of mating moving in between them to exchange with queens from their own nests. Takes resources. Nest budding allows a gradual place in the morning on still, warm days. dispersal through a habitat, and allows the colony to be adaptable to changes 2.2 Colony establishment in habitat and food resources. Social parasitism 3 Life cycle of an ant A newly mated queen flies from her natal nest and establishes a new colony Only queens lay eggs. Eggs hatch into by parasitising the nest of a different ant larvae and then undergo complete species – in the UK the host species are metamorphosis to become adult ants. Formica fusca, F. lemani and F. cunicularia. Larvae are fed a protein rich diet (insect The Wood Ant queen enters the nest prey, particularly caterpillars). Workers of the host, kills or excludes the queen move larvae and pupae around the and then uses the host workers to raise nest to the warmest areas to optimise her own offspring.