There are many thousands of ant species and most of them can be regarded as beneficial. They help control the numbers of harmful insects, dispose of carrion and remove all kinds of organic detritus. However, on their foraging expeditions ants repeatedly enter human habitations, where they may also build extensive nests. In so doing, they may hollow out walls or floors. Outdoors they undermine paths and soil with their nests.
There are three main household/indoor Ants species in South Africa:
Other species are occasionally encountered indoor and a variety outdoor.
Argentine ant (Linepithema humile): If you live in Johannesburg or Cape Town then there is a good likelihood that the ant that invades your home is the Argentine ant. It is a dark chocolate brown colour, not black. It is most easily confused with the White-footed ant Technomyrmex albipes which is becoming increasingly common in homes. This latter species is slightly smaller than the Argentine ant and is black with pale legs. The White-footed ant has an irritating habit of nesting in warm places such as electrical installations and causing them to short-circuit.
The Argentine ant was first recorded from South Africa, in Cape Town, in 1908. It is thought to have come into South Africa in fodder imported from Argentina for British cavalry fighting in the Anglo-Boer war but it is quite possible that it arrived in South Africa earlier than this. It is indigenous to Argentina but has been distributed all round the world and become a serious pest.
Nest site, under paving stones, behind tiling, in decaying logs and in the soil. Mainly active in the warm, summer months. There can be up to 100 queens in a single nest and each queen may lay 20-30 eggs a day. Egg development in about three weeks in warm periods, up to five weeks if it is cold. Larval period is about 30 days and pupal period is about three weeks.
Lepisiota capensis, a species widely distributed in Africa, and commonly found in the fynbos. It is also found quite commonly in people's homes and is pitch black, not dark chocolate brown as in Argentine ant, and not reddish coloured as in the Brown house ant. In the home it could be mistaken for the White-footed ant but the legs of the latter species are slightly pale at the base. Under the microscope they are easily distinguishable as they are in different subfamilies.
Pheidole megacephala: Light brown ants consist of workers in two sizes, where their “soldiers” have big heads; therefore they are also known as big-headed ants. Often nests under paths where it throws up small mounds of soil between paving and sometimes does not run in very definite trials and mostly active at night. Their food preferences include fats, sugar and honeydew and a colony can consists of many workers and many queens.
Carpenter ants generally aren't as destructive as termites, although large colonies are capable of causing structural damage to a house. They damage wood by hollowing it out for nesting. Carpenter ants do not eat wood like their distant cousins, the termites. Instead, they tunnel through it while building and expanding their nests. Their preferred food is honeydew, a sugar secretion of certain plant-feeding insects such as aphids and scale insects. They also feed on other plant secretions and the remains of insects, including members of their own colony. They will readily forage in the kitchen, seeking out sugars as well as fats, grease and meats.
Carpenter ants seen in a home may actually be nesting outdoors and foraging indoors for food and moisture. Stacks of firewood, stumps, logs and railroad ties are likely spots to look for nests. If outdoor nests are suspected, look around the foundation of your house at night with a flashlight, especially around doors and openings where utility pipes and wires come in the house. Seal cracks and openings in a foundation, especially where utility pipes and wires enter from the house.
The best way to control wood ants is to find and destroy their nests. Finding large nests up to 100m from the home is not uncommon. A broken bath fan hose or unvented attic creates ideal conditions under the fibreglass. Very large nests can be found in attics, and leaking plumbing vents can be a problem in both types of roofs. Sweating or leaking skylights are another concern.
A black ant or two in your house doesn't mean you have an infestation. But the fact that you've seen them nearby and now are seeing them indoors is not a good sign. They may have a nest in your house or are planning to create one
Pavement Ants are small pests (ranging from 1½ - 2½mm in length). Each individual colony contains thousands of workers, multiple queens and is usually located at one particular site.
This is a two-node ant (has two segments or nodes on its pedicel) and is dark brown in colour. Their antenna has 12 segments (which end in a 3 segmented club) and its thorax has one set of spines. The first physical characteristic noticed (when viewed under a microscope or 30 x lenses) is the lines which seem to have been sculptured on the ant's head. These grooves are evident on the head and thorax.
The pavement ant earns its name well, building nests beneath and along the sides of pavement: patios, driveways, sidewalks, foundations of homes. These pests can also be found inside of homes (and other structures) in wall voids, beneath toilets and water heaters. They also will readily nest in and beneath insulation in walls and attics. Outdoors, you will see pavement ants nesting beneath mulch, landscaping, stones and logs, and also along curbs.
The ant beds usually appear as piles of misplaced soil, without a distinctive appearance such as that of the Fire ant or Allegheny Mound Ant. These loose piles of soil occasionally will have a slight crater appearance, resembling the smaller mound of the Pyramid Ant, which always builds a small, crater-shaped mound.
Pavement ants can often be seen foraging outdoors during daylight hours, but more ant trails can be observed after dark. Upon initial inspection, the soil displaced by a pavement ant colony is usually quite evident around any outdoor concrete object: curbs, driveways, sidewalks, landscaping, brick patios, etc. In many cases, the loose soil can be seen along cracks or expansion joints of driveways and other such objects. Their colonies can also be found adjacent to the foundations or skirting of homes. When trying to locate all possible outdoor colonies, use a small hand rake to gently pull back mulching materials to expose the ants. Inspect around the edges of (and beneath, if possible) any logs or large rocks. In a sense, leave no stone unturned. In severe infestations, a number of objects can harbour many different pavement ant colonies. Each of these colonies or ant beds need to be located and treated in order to kill pavement ants and to stop their migration indoors.
When inspecting for ant trails indoors, look for foraging pests along all baseboards, near or around toilets and plumbing, and look beneath the edges of carpeting. If ant trails are found, they will need to be treated.
Pharaoh workers are very small (about 1½mm - 2mm long), light yellow to reddish brown almost transparent in colour with the abdomen (hind portion of body) somewhat darker. There is no stinger. The petiole (narrow waist between the thorax and abdomen) has two nodes and the thorax has no spines. Eyes are well-developed. The antennal segments end in a distinct club with three progressively longer segments. This is in contrast to the thief ant's two-segmented club.
Pharaoh ants do not build mounds or carve out galleries in wood. The nest in any dark void in a structure. Nest locations include wall voids, cabinet voids, behind baseboards and window mouldings, behind insulation of appliances, inside hollow curtain and shower rods, boxes and expansion joints in slabs. They may even be found in areas such as folded paper sacks and newspapers. Outside, these ants can be found in leaf litter, flower pots and in the debris of rain gutters.
Unlike most ants the Pharaoh ant is polygynous, meaning its colonies contain many queens (from 2 to over 200). Pharaoh ant colonies can grow large enough to contain as many as 300,000 workers Colonies also lack nest-mate recognition so there is no hostility between neighbouring colonies. Colonies reproduce by 'budding', where a subset of the colony including queens, workers and brood (eggs, larvae and pupae) leave the main colony for an alternative nest site. Budding is the major factor underlying the invasiveness of Pharaoh ants. A single seed colony can populate a large office block, almost to the exclusion of all other insect pests, in less than six months. Elimination and control are made difficult because multiple colonies can also contract into smaller colonies and 'weather the storm' of a baiting programme only to rebound when baiting is withdrawn. The queens are very mobile and so are the colonies. This is a key point to remember when attempting to eliminate infestations.
Pharaoh ant elimination can only be accomplished through an extensive indoor baiting program. Indoor treatments with residual insecticides will not eliminate an infestation of these ants. Only about 5% of a Pharaoh ant colony's workers are out foraging for food at any one time. By attempting to kill ants with a spray, the remaining 95% of the workers will become stressed and split into two or more new colonies.
In severe infestations of larger buildings, total elimination of Pharaoh ants has been known to take up to a year. Because of the particular habits of this pest, your baiting program should extend for several months.