Ants are fascinating eusocial insects related to bees and wasps (Hymenoptera). They live in nests that contain many hundreds and sometimes thousands of ants. Most are wingless sterile females, known as workers, but there will also be fertile females (queens), and males. More than 30 species of ant are found in Britain, a few of these can occur in gardens, including the familiar black garden ant, Lasius niger.  

Ants are one of the most numerous animals and important components of ecosystems worldwide affecting fauna and flora of entire ecosystems. In gardens they can be important predators, but also manage greenfly and other aphids and can cause soil disturbance.

Find out more about UK ant species from the Bees, Wasps and Ants Recording Society (BWARS).
 

Ants can cause concern but they are an important part of the biodiversity of a healthy garden. The eusocial nest structure can be complex with different casts and ages of worker ants. They often have mutualistic associations with sap sucking insects such as aphids. 

• Ants feed mainly on other invertebrates, including other ants
• They also collect the sweet liquid known as honeydew, which is excreted by aphids and some other sap-feeding insects
• Ants can protect aphids from ladybirds and other predators in order to secure their supply of honeydew. Increased numbers of aphids may result in more damage to plants
• Ants do little direct damage to plants, although they can disturb soil around plant roots and deposit it on the surface during their nest building activities. This can be an issue on lawns and where low-growing plants are being buried by excavated soil. They may also disturb plant roots in pots and containers. This disturbance can also mean that plants are more prone to wilting especially when dry at the roots
• Sometimes ants will nest in a compost heap or bin. They will not be causing any damage in this situation
• Some ants (mostly Myrmica species - commonly known as red ants) can sting, but for most people this is no more than a minor irritation

When choosing management options you can minimise harm to non-target animals by starting with the methods in the non-pesticide management section. In most cases this should mitigate the problem and pesticide control of ants in gardens is not necessary.

Non-pesticide

• Ants should be tolerated in gardens wherever possible, they do not cause direct damage to garden plants and are an important part of the biodiversity gardens can support. They predate many other invertebrates
• Unless nests are particularly troublesome, ants are best left alone. If a colony is destroyed it is likely that its place will be taken by in-coming queen ants, which take over the territory and may establish even more new nests
• Disperse ant heaps on lawns by brushing the excavated soil on a dry day before the lawn is mown, otherwise the soil will get smeared on the lawn surface by the mower
• If the lawn has an uneven surface due to years of ant activity, peel back the turf in the raised areas, remove excess soil and relay the turf. This is easier to do in the winter when ants are less active
• A pathogenic nematode, Steinernema feltiae, is available from some suppliers of biological controls for treating ant nests in lawns and flower beds. The microscopic, worm-like nematodes are watered into the soil in places where ants are bringing soil up onto the surface. This nematode may also affect non-target insects

Pesticides 

• Ant control with pesticides in gardens is unnecessary impractical and ineffective. Pesticide use will also potentially harm other non-target animals having a detrimental effect on garden health
• Many proprietary ant powders, baits, sprays and aerosols are available for controlling ants in and near buildings, these are not suitable for garden use or application on plants or soil and can have a detrimental effect 

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Biological control suppliers (downloads pdf document)

Ant nests contain one or more fertile female queen ants, which lay eggs in brood chambers within the nest. Most of the other ants in a nest are smaller wingless sterile females, which are known as worker ants. Their role is to maintain, guard and enlarge the nest, feed the larvae and gather food for the colony.

• The white maggot-like larvae are fed on a liquid diet secreted by worker ants
• When fully fed, the larvae turn into pupae
• Some species of ants pupate inside spindle-shaped whitish-brown silk cocoons. These cocoons are often referred to as 'ant eggs'. The real eggs are very small and not easily seen with the naked eye
• At certain times of year, ant nests produce winged ants. These are young queens and male ants, which often emerge en masse (often labelled 'flying ant day', the mating masses can be picked up by weather radar) from nests during humid weather in the summer. These fly up and mate, after which the males die and the young queens try to find suitable places where they can establish new nests
• Once mated, the queen ant no longer needs wings, so they are bitten off