Big Headed Ants (BHA)

Introduction

These ants get their common name from the exceptionally large head of the major workers in relation to their body size. Various species are found throughout the United States including Hawaii. A few species serve as intermediate hosts of tapeworms which infect turkeys, chickens, and domestic fowl.

Recognition

Workers dimorphic (2 species polymorphic, one each SW Texas, southern Arizona), 1/16-1/4″ (1.5-6 mm) long with minors usually about half as long as majors; queens longer than majors. Color ranges from yellowish to light brown to yellowish red to dark reddish brown, some species with areas of dark red and/or black. Major worker with head exceptionally large in relation to body size. Antenna 12- segmented, with 3-segmented club. Thorax with 2 spines on upper back; profile unevenly rounded. Pedicel 2-segmented. Stinger present. Workers of some species emit an odor of mammalian feces when alarmed.

Similar Groups

1. Fire ant (Solenopsis spp.) have antenna 10-segmented with 2-segmented club, thorax lacks spines.
2. Pharaoh ant (Monomorium pharaonis) with thorax lacking spines, no major worker caste.

Biology

Depending on the species, mature colonies range from small to large. The majority of species form small colonies, numbering about 200-300 individuals; species forming large colonies may number up to 2,000-3,000 individuals. Colonies are multi-queened. The large heads and associated large mandibles of the major workers are utilized to crack the husks of seeds and/or the hard exoskeletons of insect prey. Several species stridulate (make sounds) when alarmed and/or when food is found which functions to attract more ants to the stridulating ant(s).

A few species serve as intermediate hosts of tapeworms. For example, P. bicarinata Mayr (Nebraska to New York and south to Arizona and Florida) is an intermediate host of the tapeworm Raillietina georgieuis Reid & Nugara of wild and domestic turkeys, of the chicken tapeworm R. echinobothrida (Megnin), and of the domestic fowl tapeworm R. tetragona (Molin).

Habits

Bigheaded ants only occasionally invade structures and usually nest in the soil surrounding structures. Most species nest in the soil in protected situations such as under stones, patio blocks, slabs, firewood, and landscape timbers, although they will nest in open areas where they make small mounds. It is not uncommon to find them nesting under leaf litter or mulch around building foundations. A few species will nest in rotting wood and stumps. With regard to structures, bigheaded ants will often nest under slabs and enter the structure via expansion joints and cracks in the slab. They will occasionally nest in crawl spaces, and are known to utilize termite-damaged wood for nesting purposes.

Bigheaded ants feed primarily on seeds and insects, and occasionally on honeydew. In homes, they will feed on meats, grease, liver, molasses, peanut butter, and fruit juices. They usually show a preference for high-protein foods.

These ants readily trail. Although they usually do not trail far from their nest, the senior author observed two colonies in Florida foraging over 150 feet (46 m). From their outdoor nests, one trail went up a palm tree trunk and down its leaves in contact with the second floor of the motel, then down a long hall to raid the food trays left in the hallway overnight. The second trail came up two flights of stairs to raid similar food trays in another of the motel buildings. In both cases, the trail down the hallway was under the edge of indoor-outdoor carpeting.

Ants Pest Control Naples

If the ant trail can be followed back to the nest, then treat the nest with an appropriately labeled pesticide. If the ants are coming out of wood or a slab expansion joint or crack, injecting pesticide from a high-pressure (160 psi) aerosol is very effective. If the trail disappears into a wall void, apply a dust (better) or aerosol via access through electrical outlet or plumbing installation holes; drill for access only as a last resort.

If the colony cannot be located, baiting may be necessary. In general, high-protein baits work best, but also try sweet baits.

For areas where bigheaded ants are common, a perimeter treatment utilizing a microencapsulated or wettable powder formulation of pyrethroid is advisable. Be sure that no shrub or tree branches are in contact with the structure.