Black Ant - Fact File

Black Ant Size: Workers 5mm overall body length. Queens about 15mm
Markings: Varies in colour, usually dark brown/black.
Location: Numerous habitats - houses gardens, factories, etc.
Detection: Visual sightings of adults often the first indication. Some earth excavation around wall edges and paving slabs also a sign. 'Ant eggs' (pupae) under stones etc. shows nest site.

This is one of the commonest British ants, found in almost all parts of the country. A hymenopterous insect, the ant enters properties through cracks in brickwork and around/under windows and doors in search of a meal. It causes annoyance when found feeding on our food, often causing people to throw away products found to be infested. However, they are not known to carry disease organisms.


The ubiquitous ants make their nest in the soil, on grassland including lawns, at the base of walls, under flat stones and sometimes in hollow trees. Nests are often very numerous near buildings and occasionally may be situated close to or actually in the foundations.

The foraging workers follow fairly well defined trails to their feeding grounds which may be many yards from the nest. They have varied feeding habits. They may enter buildings, often through very narrow crevices, and if food, especially sweet food, is found by one ant there will soon be many others to share the feast. Houses, restaurants and food shops, office buildings and hospitals etc. may be entered this way and the ants may cause a considerable nuisance and some damage but their nests are usually outside the buildings.

Much can be written about their lifecycle, but it is suggested that the reader takes time to seek out more information on these insects. One of the most annoying stages is the mating period itself. During the summer great numbers of winged females (which are potential queens) and males are reared in the nest and on one or two warm summer afternoons between mid-July and mid-September they swarm out and take to flight often in quite spectacular numbers. This usually happens simultaneously over a wide area of country. Sometimes, if a nest is situated in the foundations, these winged ants may swarm inside buildings. Sufferers may take comfort in the knowledge that the trouble will soon cease. During the flight, the ants mate. Many thousands are eaten by birds and in about two or Three hours it is all over; the survivors return to earth, the males soon die, the queens shed their wings and make themselves a cell, generally in the soil where they pass the winter before attempting to start a new nest the following spring. A few - but enough - succeed. Some may find shelter in existing nests but these will generally only tolerate one queen. Under favourable conditions the queen and therefore her nest, may survive for several years.


In all cases, only by finding the nest can a control method be guaranteed. Removal of attractant foodstuffs must also be considered. Use of insecticides outdoors.

Usually the nest will be situated under a path within about 6m (20ft) of the house. The precise location can often be discovered by following a trail of ants and if the nest can then be exposed, it can be treated directly. Ensure your chosen insecticide is approved for use in such situations. Where there is risk that plants may be damaged by such treatment, an insecticide dust or spray labelled for horticultural used should be chosen (check your qualifications for using these chemicals). If the nest cannot be found, an insecticide dust or spray may be applied around doors and window frames, ventilators and waste pipes to make a barrier to prevent entry into the house. Carbamates are particularly effective against all species of hymenoptera, including the ants.

Use of insecticides indoors

Where it is impracticable or impossible to prevent ants from entering, sprays, dusts or an aerosol/ fogger suitable for the control of crawling insects may be used indoors. Application should be in the form of continuous bands around points of entry, along skirting boards, etc. Don't contaminate food/ preparation surfaces with the insecticide. Similarly, insecticidal dust may be sprinkled around points of entry and into cracks. Swarms of flying ants may be a nuisance but they are harmless. In such instances, the problem may be overcome by the use of a flying insect aerosol or a space spray such as a Microgen.

Black ants are of little public health significance and many companies / authorities do not include them in their lists of normally treated pests. However, they are a considerable nuisance, and much work can be had from ant control.

If you need a fast, effective and reliable pest controller in the Bishops Stortford area
contact Cross Pest Control on:
Hertfordshire: 01920 822897
Mobile: 0777 5673088 or 0777 5673089