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This ant is now a major pest throughout most of Florida and several of the Hawaiian Islands. It occasionally is found in apartments and greenhouses in northern states. These ants nest outdoors under items on the ground, within landscape mulch, beneath loose bark on trees, under ground cover, in potted plants, and within piles of items such as lumber, firewood, or bricks. Nests may be readily established inside homes in walls, beneath carpeting, and in other suitable voids or spaces.
Ghost ant workers are extremely small, 1.3 to 1.5 mm long and monomorphic (one-sized). They have 12-segmented antennae with the segments gradually thickening towards the tip. Antennal scapes surpass the occipital border. Head and thorax are a deep dark brown with gaster and legs
opaque or milky white. The thorax is spineless The gaster (swollen part of abdomen) has a slit-like anal opening which is hairless. The abdominal pedicel (stalk-like structure immediately anterior to the gaster) consists of one segment which is usually hidden from view dorsally by the gaster. Stingers are absent. The small size, combined with the pale color, make ghost ant workers hard to see.
Biology and Behavior
Ghost ants may develop huge colonies containing thousands of workers and numerous queens. This species may be difficult to control and does not feed much on ant baits. The keys to control are to find the colonies and subcolonies and treat them directly. Regular inspections and service are necessary to find and treat new colonies as they move from neighboring properties.
This species is a household pest. In Florida, it is considered one of the most important of such ant pests. The ghost ant can not only invade houses from outside, but they can nest in the house as well. Although the ant feeds upon many household foods, it seems to show a preference for sweets, having been observed feeding on sugar, cakes, and syrups. Outside, the workers scavenge for dead insects and tend sap-sucking insects, collecting honeydew. Foragers are seen in kitchens and bathrooms on sinks, counters, and floors. When crushed, the workers emit an odor similar to that of rotten coconuts.
The ghost ant is highly adaptable in its nesting habits. It nests readily outdoors or indoors. Colonies may be moderate to large in size containing numerous reproducing females. Generally, the colonies occupy local sites that are too small or unstable to support entire large colonies. The sites include tufts of dead but temporarily moist grass, plant stems, and cavities beneath detritus in open, rapidly changing habitats. Indoors, the ant colonizes wall void or spaces between cabinetry and baseboards. It will also nest in potted plants. Thus, the colonies are broken into subunits that occupy different nest sites and exchange individuals back and forth along odor trails. Ghost ants are opportunistic nesters in places that sometimes remain habitable for only a few days or weeks.
Multiple queens may be spread out in multiple subcolonies. Usually, nesting occurs in disturbed areas, in flowerpots, under objects on the ground, under loose bark, and at the bases of palm fronds. Indoors, the ant nests in small spaces such as cracks, spaces between books, or wall voids. Indoor foragers often come from outside. This is a very common pest inside homes.
New colonies are probably formed by budding. This occurs when one or more reproductive females, accompanied by several workers and possibly some brood (larvae and pupae) leave an established colony for a new nesting site. There does not appear to be any infighting between members of different colonies or nests.
Workers have the habit of running rapidly and erratically when disturbed. They are fond of honeydew and tend honeydew-excreting insects. They also feed on both dead and live insects. When workers are found trailing, their movement is more slow and deliberate. On close inspection some trailing workers can be seen carrying brood (larvae and pupae). They will enter structures from nests near foundations or from plants that contact the building.
Control
This species may be difficult to control and ant baits may not be effective against it. The keys to control are to find the colonies and subcolonies and treat them directly. Where the colonies cannot be found, baits may be attempted; however, several baits may be required before positive results are seen. Regular inspections and service are necessary to find and treat new colonies as they move in from neighboring properties.
The best approach to ant control in the home is cleanliness. Any type of food or food particles can attract and provide food for ants. Store food in tight containers. Remove plants that can attract ants or control aphids, whiteflies and other insects that produce honeydew. Reduce moisture sources, including condensation and leaks.
Indoor colonies nesting within voids can be controlled with baits. Access of foragers entering from outdoors through cracks and crevices or screens should be restricted with barrier sprays. Residual and systemic sprays to vegetation surrounding structures can also help by eliminating honeydew producing insects. A key aspect of control involves trimming trees and shrubs surrounding the structure to stop ants from "bridging" (trailing from the vegetation onto the structure). The best policy is to not have any vegetation touching exterior walls. Large trees which overhang the structure should also be trimmed back to stop "leaf nests" from falling onto roofs which can cause reinfestation of the building. Vegetation favored by Ghost ants in south Florida includes: nearly all palms, especially coconut, sable, or queen, most fruit trees, large ficus trees, gardenia, hibiscus,
ixora, many plants having showy flowers with sweet nectars and most plants which are infested with aphids, scales, mealybugs or other sap-sucking insects.
General tips for limiting ant infestations include:
Eliminate piles of lumber, bricks, or other debris that could serve as a nesting site for ants.
Keep landscape mulch less than 2 inches thick and at least 12 inches away from foundations.
Ensure the sprinkler system does not spray directly onto the foundation.
Seal as many cracks in the home's exterior as possible.
Keep tree and shrub branches from touching the house.
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