Pharaoh's Ants

 

Pharaoh ants will prefer to nest in a warm (25°C) and humid (80%) environment and they will also choose areas which are near sources of food and/or water. These nests are usually situated in inaccessible areas such as wall voids, behind skirting boards, in furniture, under floors and between linens making them extremely difficult to locate and control. This is a trail-making ant that can spread disease mechanically. Pharaoh ants are a polygynous species meaning each colony will contain many queens which in turn leads to unique caste interactions and colony dynamics.  Due to this they are also able to fragment into bud colonies extremely quickly known as “budding”. This is the action where a queen will break off from the colony with some workers and start a new colony nearby, especially if they feel threatened.

Although Pharaoh ants are a tropical species, they will happily thrive pretty much in any building even in cooler regions providing there is central heating.  

Identification:
Workers are only 2mm long whereas the Queen will be around 5mm long and both are yellow in colour with darker markings on the abdomen. In the UK and its cooler climate, it is primarily an indoor species associated particularly with large facilities such as hospitals, and blocks of flats and prisons. Pharaoh's ants will travel through ducts and walls etc to look for food and may carry disease organisms which will in turn contaminate wounds and sterile materials, which is especially important in hospital environments. Their ability to travel through ducting and buildings means infestations can become very widespread very quickly and difficult to control.

Biology:
The egg to adult stage is reached in around 5 to 6 weeks. Colonies tend to be very large with the workers often numbering to several thousand. There are usually several hundred reproductive females present in a colony so when a nest gets too large to accommodate all the ants, young Queens, and several support workers leave the colony and find alternative nesting sites. This is known as "budding”, and the new colonies are often called satellite nests.

Workers only live about ten weeks, with only up to 10% out foraging at any given time for food/water. The Queens can live up to 12 months whereas the males die within about 3 to 5 weeks after mating. Queens lay approx. 350 eggs in batches of 10-12, larvae hatch after 2 weeks and are fed by workers, after several skin changes pupation takes place. Full-grown ants hatch soon afterwards depending on temperature.

Control:
Due to the budding system employed by these ants, the use of insecticide sprays and powders against them is not recommended. The chemicals in them cause nests to split up and as the nests can contain several queens this can result in a single nest splitting up to become several satellite nests and in the long-term making matters far worse. Successful control can only be accomplished by using baits that worker ants feed on and then take back to the nest to feed the queens and juvenile stages. This also does not cause any distress and reduces the risk of them splitting.  Baits can either contain small amounts of a poison that will kill the ants after a short period of time or some have insect hormone that disrupts the breeding success of the queens and prevents the juvenile ants from developing properly into adulthood.

Complete eradication can take up to 13 weeks using the described control methods, although a reduction in ant numbers should be noticed after 1 month.   Treatment should not cease until your 100% sure there are no new nests so baits should be replenished and widespread to ensure total control.

Thorough documentation as to where and when baits are laid should be carried out to have a true idea of the treatment success.

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