An overview of the unusual characteristics of the white-footed ant, with tips for gaining control.

White-footed house ants (pictured above) can be one of the trickiest indoor ants to control. They are not so difficult to control outdoors, as they can be prevented from coming inside by a thorough perimeter treatment and spraying foraging trails, preferably with a non-repellent spray. But when they are nesting indoors and baits need to be used, their unique colony structure makes control problematic.

There are actually several species that form the white-footed ant complex, with Technomyrmex albipes and Technomyrmex difficilis being the two most common. Outside they will build their nests out of debris on the ground and in bushes and trees. They are typically arboreal, where they prefer to feed on the honeydew of sap-sucking insects. Inside buildings, they are equally happy to build their nests in wall voids and among the insulation in roof voids. To control white-footed ants in these indoor locations, it makes sense to choose your favourite sugar-based bait, but it may take longer than you would expect to get control.

“Kill the queen and you kill the colony” is the mantra for ant control treatments. The problem with white-footed ants is that nearly half the colony is made up of intercastes – fertile, reproductive females – and you will need to kill them all to eliminate the colony. But intercastes are only part of the interesting colony structure…

White-footed ants have a mating flight, when males and females will pair up during the nuptial flight and found new colonies. As the nest develops, the queen will start to produce intercastes. These intercastes are inseminated by wingless males that are also produced, greatly increasing the reproductive capacity of the colony. With all these intercastes, there is no impact on the colony when the dealate queen dies. Although the white-footed ant does produce alates for a nuptial flight, new colonies can also be produced by budding. In an established indoor infestation, it is quite likely there will be a number of nests within the structure and there is often movement between nests.

White-footed ants also have an unusual method for sharing food within the colony. There is certainly some debate around the extent of trophallaxis that occurs within white-footed ant colonies. Instead, it appears that the food brought back by the foragers is shared later through the laying of tropic (non-viable) eggs. These trophic eggs are then fed to other ants within the colony. If the bait is too fast acting, there is a danger that the foragers may die before laying trophic eggs. But assuming that trophic eggs are laid, the passing of food within the colony is a more convoluted process in white-footed ants.

So, to eradicate white-footed house ants with baits, it’s firstly very important to find all the nests in the structure. Although there may well be movement between these nests, it is important to bait each trail/nest separately.

Secondly, given the number of reproductives in the colony and indeed the total number of ants present in large infestations, it is important to place sufficient bait to ensure the bait is spread through the colony to all the reproductives.

Thirdly, finding all the nests and gauging how much bait to apply is time-consuming work, so it is often wise to allow for at least one follow-up visit, to either apply more bait or check for eradication to ensure there is no rebound from surviving reproductives.

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