Workers are all the
Thorax uneven in
shape when viewed
from side with no spines
Because of their very small size, Pharaoh ants are often
considered a minor pest but if they are ignored they can multiply rapidly
and become a serious risk to health. They are one of the most difficult
pests to eliminate in structures requiring the training and experience of a
professional. Pesticide sprays will only worsen the problem.
Up to 300,000 workers with multiple queens
will nest in wall and cabinet voids, behind
baseboards, behind refrigerator insulation, inside hollow curtain rods, or
in the folds of sheets, clothes, or paper. They follow plumbing and
wiring and have been found in light switches and electrical outlets.
In colder climates they prefer to nest in heated buildings.
Colonies are very mobile;
workers, along with larvae, pupae, and even a few queens, may move to new
locations if disturbed or if colony becomes too large.
New nests can be formed by "budding" with as few as
5 workers, 10 preadults, and one queen migrating from the original colony.
Development time (egg to adult) for workers is about 38 days at 80 degrees
F. Workers live about 9-10 weeks, with only up to 10% out foraging at any
given time. Queens live about 4-12 months, and males die about 3-5 weeks
In some areas, this ant has become a major
pest of residences, food plants, factories, office
buildings, apartments, and hospitals. Infestations
in hospitals have become a chronic problem in Europe and the United States
where burn victims and newborns are subjected to
increased risk because the Pharaoh ant can transmit over a dozen pathogenic
pathogens. Pharaoh ants have been observed seeking
moisture from the mouths of sleeping infants and from in-use IV bottles.
Control of Pharaoh ants is difficult, due to their nesting in inaccessible
areas. Treatment must be thorough and complete at all nesting sites, as well
as the foraging area. Thus, treatment must include walls, ceilings, floor
voids, and electrical wall outlets. Baits are now the preferred method of
control for Pharaoh ants and several baits (insecticides) are labelled for
indoor ant control. A Pharaoh ant infestation of a multifamily building
requires treatment of the entire building to control the infestation. Ants
nesting on the outside may be controlled by also using a perimeter barrier
Baits cannot be placed in just any location and be
expected to work. Pharaoh ant trails and their resources (both food and
water) must be located for proper placement of baits and effective control.
Non-repellent baits (such as boric acid, hydramethylon or sulfonamide)
should be used, as repellent baits can worsen the situation by causing the
colony to fracture and bud. As a result, ant activity will briefly diminish
as as the new colonies establish themselves, then again become a problem as
the foragers resume activity in a new location.
An extensive baiting program, combined with exclusion and
sanitary practices, is the best way to manage pharaoh ant populations.
Insecticide sprays will only make infestations worse by dispersing colonies
to new locations. Be sure to distinguish pharaoh ants from thief ants which
are similar looking but not as easy to control with baits.
invade your home, take immediate action
- Sponge invaders with soapy water
as soon as you see them.
- Plug up ant entryways with caulk
or petroleum jelly.
- Clean up food sources such as
sugary spills, pet food, or garbage.
- Rely on baits to control the ant
colony but choosing the wrong one could worsen the problem.
- Insecticide sprays are not
effective for pharaoh ants.
- If you are not prepared for failure, call a