Name: Thief Ant
Latin Name: Solenopsis molesta
Nicknames/common names: Grease Ant
Thief ants steal food from other ants, sometimes parasitically forming colonies inside the nests of other ants. Thief ants are also called Grease ants because they are attracted to, and consume greasy substances.
How do you get rid of Thief ants?
Thief ants can be troublesome when they get into human dwellings. It is often difficult to find these ants due to their inaccessible and remote nesting areas and their minuscule size. They are also not always present in the vicinity of their colony because they tend to travel far to find food. They are small enough to enter into things that other insects can’t. The easiest way to locate a colony is to look for trails of ants. Thief ants are not attracted to common ant traps and appear to be resistant to most insecticides, quickly causing the colony to bud and initiate satellites.
How to identify Thief Ants
Thief ants are the smallest ants in Ontario, ranging from 0.5-3 mm long; queens are around 4-5 mm long. Often yellow, or yellow-brown, these ants have a two-segmented petiole connecting abdomen and thorax. They have ten segments in their antennae, which end in large segmented clubs. Thief ants have small eyes and workers have massive jaws for carrying food back to the colony.
Life stages & anatomy
Mating typically takes place from July to late fall; winged princess ants will sometimes embark on their nuptial flight with a worker or two clinging to their bodies who will aid the new queen in excavating its nest when it finds a suitable place for a colony. Thief ant queens can lay between 27 and 387 eggs per day, and with about a 52 day maturation time, thief ants proliferate quite rapidly.
Distinguishing features/insects resembling Thief ants
Thief ants are often mistaken for being Pharaoh ants due to their similar size and colouration. Several differences can be viewed under a microscope, but two readily accessible differentiations are that 1) Thief ants have small stingers on their abdomen, Pharaoh ants do not and 2) When they die Thief ants curl up into a ball, Pharaoh ants do not.
Signs of a Pest Name Infestation
Where did they come from / how did I get them?
Thief ant colonies contain anywhere from a few to a few hundred thousand workers and can survive just about anywhere: In cracks in structures, under the floorboards of your kitchen, in the soil beneath rocks and other garden debris, or in an existing colony. Their nests, which are large for their body size, typically contain access tunnels to neighbouring colonies that serve as stable food sources to steal from. Like many of the ants on this list that are attracted to human habitations, thief ant colonies have multiple queens. Interestingly, colonies with a reliable and ready food source don’t have as many workers because food is readily available. Ants of this species are so small that they often go unnoticed inside human habitations.
What do Thief ants eat?
Astonishingly, thief ant colonies can sometimes be found inside of other ant colonies and will feed on the larvae and pupae of their host ants. Thief ants can travel considerable distances for food, and like other ants, they will mark pheromone trails to guide fellow workers towards just about anything edible, including grease, dead animals and fungal spores. Unlike most ants, thief ants do not appear to be attracted to sugar.
How Addison can help Prevent Thief Ant Infestations in the Future:
Inspect all incoming plant and organic matter before establishing it on your property or bringing it into your home. Even if the origin of an infestation is rooted out, it is important to be stringent in your implementation of physical controls; fill cracks in building facades, and seal window frames (refit if necessary). Keep outdoor spaces dry and open to sunlight, clear debris that creates humid and moist conditions for ant colony-building, and lift firewood off the ground. Establish a perimeter clear of organic matter of at least 1ft around the structure. Shrubs and tree branches should be cut back from your home to limit access points to the structure. Inside, kitchens should be kept clear of spills and crumbs; food should be kept tightly sealed, keep organic waste in the freezer, seal moisture drips and leaks from drains and plumbing, repair cracks and fissures in floors and walls. Most ants who invade homes tend to be ‘budding’ members of larger colonies that are working to establish smaller satellite nests. It is important to inspect moist and decaying wood and wood structures like decks, porches, sheds, playsets on your property and to remove any dilapidated structures or potential harbourages.