What Kind of Ant is This?
Lisa Lennon, Extension Agent – IPM (Fire Ant Project) for Travis and Williamson Counties
Texas AgriLife Extension Service  

Ants are not all created equal. There are many species in Texas and it just takes some persistence and knowing what to look for to tell them apart. Most people think that only imported fire ants are around. But if you look closely and take time to learn a little ant biology, the ant world can be a captivating place. Red imported fire ants are real pests, with few natural enemies in the United States. Many other ants live here too, but most are not considered serious pests, although any ant may be considered to be a nuisance when locally abundant. In fact, some native ants are in constant competition with the imported fire ants and may even help humans in the war against this invading species.

Native and exotic “desirable” ant species that compete with fire ants are sometimes difficult to identify, but once their characteristics and habitats are revealed, most are easy to spot – and perhaps even use them to our advantage against imported fire ants. Described below are some common competitor ant species, how to identify them, what their nest looks like, where they live, and what they eat (Hodges, S. A.1992):

Pyramid Ant, Dorymyrmex spp.

The pyramid ant is a small ant about 1/8″ long. Key identifying feature is a pyramid-shaped projection on top of the thorax. They are red-black or dark brown. It builds its nests in open, sunny areas. The workers deposit the soil in a circular crater or mound around the entrance hole and are usually 2 to 4 inches in diameter. These mounds are usually located near the nests of other ants, particularly harvester ants. The colonies can also be found under decorative rocks and logs. Workers move quickly and forage in ready trails. They feed on other insects and are fond of the honeydew produced by aphids and scales.

Bigheaded ant, Pheidole spp.

Bigheaded ants have two sizes: workers – major workers (soldiers) and minor workers. Major workers have a very large head in proportion to their bodies. Bigheaded ants are most often confused with fire ants, but imported fire ants do not have workers with larger heads. Bigheaded ants usually nest in the soil in protected locations such as under rocks, logs, firewood, patio blocks and landscape timbers, although they will nest in open areas of soil. They typically feed on live and dead insects, seeds and the honeydew produced by insects such as aphids and scales. They are considered major predators of fire ant queens which are present in large numbers following a fire ant swarm.

 

Common House-infesting Pest Ants (from Drees, 1998)

Pharaoh ant, Monomorium pharaonis

Also called “sugar ants” or “piss ants,” pharaoh ants are some of the smallest ants, about 1/12-1/16 inch long, with a light tan to reddish body. pharaoh ants are the most commonly occurring indoor ant in Texas. In hospitals it has been suspected to be a carrier of more than a dozen pathogenic bacteria including Staphylococcus, Salmonella, Pseudomonas andClostridium. These ants do not sting and usually do not bite. Pharaoh ants are omnivorous, feeding on sweets (jelly, particularly mint apple jelly, sugar, honey, etc.), cakes and breads, and greasy or fatty foods (pies, butter, liver and bacon). Nests are rarely found outdoors and almost anywhere indoors (light sockets, potted plants, wall voids, attics, in any cracks and crevices) particularly close to sources of warmth and water.

Life cycle: Complete metamorphosis. Development of worker ants progresses from a egg (5-6 days), to several larval stages (22-24 days), a prepupal stage (2 to 3 days), through a pupal stage (9-12 days) to an adult ant, thus taking from 38 to 45 days from egg to adult (4 days longer for sexual forms).

Colonies consist of one to several hundred queen ants, sterile female worker ants, periodically produced winged male and female reproductive ants (sexuals) and brood (developmental stages). These ants do not swarm. Colonies multiply by “budding”, whereby a large part of an existing colony migrates carrying brood to a new nesting site.

Carpenter ants, Camponotus sp.

Fourteen species of carpenter ants occur in Texas. The largest species is the black carpenter ant, Camponotus pennsylvanicus, which is found primarily in wooded areas outdoors. Common indoor species, Camponotus rasilis and C. sayi, have workers that are dull red bodied with black abdomens. Worker ants range in size from 1/4 to 1/2 inch. They can be distinguished from most other large ant species because the top of the thorax is evenly convex and bears no spines. Also the attachment between the thorax and abdomen (pedicel) has but a single flattened segment. Although these ants can bite, they do not sting. Galleries excavated in wood to produce nesting sites can weaken structures. Foraging worker ants in the home can be a nuisance. These ants usually nest in dead wood, either outdoors in old stumps and dead parts of trees and around homes (in fences, firewood, etc.) or indoors (between wood shingles, in siding, beams, joists, fascia boards, etc.). Ant colonies are often located in cracks and crevices between structural timbers, but the ants can also tunnel into structural wood to form nesting galleries – although this is rare for species occurring in Texas. They often appear to prefer moist, decaying wood, wood with dry rot or old termite galleries. However, damage is often limited because these ants tunnel into wood only to form nests and do not eat wood. Galleries (nesting tunnels) produced by carpenter ants usually follow the grain of the wood and around the annual rings. Tunnel walls are clean and smooth. Nests can be located by searching for piles of sawdust-like wood scrapings (frass) underneath exit holes. These piles accumulate as the nests are excavated and usually also contain parts of dead colony members. Occasionally carpenter ants, particularlyCamponotus rasilis Wheeler, nest under stones or in other non-wood cracks and crevices. Foraging worker ants leave the nest and seek sources of sweets and other foods such as decaying fruit, insects and sweet exudates from aphids or other sucking insects. Life cycle: Development from egg to worker ant occurs in about 2 months.

Carpenter ants are social insects and live in colonies made of different forms of ants or “castes”. Mature colonies contain winged male and female forms (reproductives), sterile female workers of various sizes, and a wingless 9/16 inch long queen. Winged forms swarm during May through late July. The presence of 3/4 inch long winged forms in the home is an indication that structural damage may be occurring.

Crazy ant, Paratrechina longicornis

Crazy ants are small, dark grey to black ants easily recognized by their extremely long legs and antennae. Crazy ants get their name from their habit of running about erratically with no apparent sense of direction. Colonies can most often be found living in soil, under items such as logs, stones, landscape timbers, wood, debris, and living under above-ground swimming pools. Crazy ants feed on a wide variety of foods, including other insects, grease, and sweets. They have been known to feed on the larvae of fleas and flies, and also have been observed carrying away fire ant queens immediately following a swarm.

Workers of the crazy ant are fast-running grayish black ants with long legs and antennae. Although they nest primarily outdoors, they will forage in homes. They are omnivorous, but are difficult to attract to ant baits.

Other Common Ants

A number of other ant species are occasionally encountered in and around the home. Theacrobat ant, Crematogaster sp., nests under stones, in stumps or dead wood and occasionally invade the home. Some species make carton nests in trees. These ants have a heart-shaped abdomen that is often held up over their bodies. They feed primarily on honeydew produced by aphids.

Argentine ant, Iridomyrmex humilus, workers are light to dark brown and generally nest outdoors. It is not common in areas infested by the red imported fire ant. Bigheaded ants, Pheidole species, have major worker ants with relatively large heads compared to their bodies. They have 12-segmented antennae with a three-segmented club. Their habits are similar to red imported fire ants, feeding on live and dead insects, seeds and honeydew outdoors and greasy food sources and sweets indoors.

The little black ant, Monomorium minimum is a slow-moving small and shiny black ant. Workers prey on insects and feed on honeydew produced by sucking types of insects such as aphids. Workers of the odorous house ant, Tapinoma sessile look somewhat like red imported fire ants, but have a pungent “rotten coconutlike” smell when crushed. Workers oftramp ants, Tetramorium species (e.g., T. bicarinatum), also resemble the fire ant, but on close examination the head and thorax are roughened with parallel grooves rather than being smooth. The ghost ant,Tapinoma melanocephalum, is also becoming a problem in Texas.

Common Turfgrass Ants (from Drees et. al 1993)

Several other species of ants occasionally cause concern. (see Table to identify turfgrass pests). Many of these species are native to the state and are not considered to be major pests. Pyramid ants are grayish black and produce small mounds featuring an edge or rim around the top. These ants are not harmful. Another native species, the little black ant, is common and its colonies are seldom encountered. This species is known to prey upon the queens of the red imported fire ant. Although the red harvester ant produces denuded areas of coarse soil particles around the central openings to its colonies, this native species is seldom harmful. Harvester ants can bite and sting and can be dangerous to sensitive individuals. These ants also serve as food for the ever rarer horned toad.

Texas leaf-cutting ants produce numerous hills or “towns” around their colony sites. These ants harvest vegetation on which to grow a fungus, and then feed on the fungus. The leaf-cutting ant is not very common, but colonies can be a problem in turfgrass areas. Although vegetation can be protected by repeated applications of contact insecticides, eliminating the colony is the only way to prevent recurring damage. There are few methods of safely eliminating colonies.

Little black ant, Monomorium minimum
Little black ants are very small black ants and closely related to the Pharaoh ant (an indoor pest ant). They nest in soil under rocks, logs, or debris and build nests in open areas of soil in lawns. The nests in the ground are small craters of very fine soil. Their colonies will also be found under the bark of trees, in debris trapped in the crotches of trees, and in wood damaged by termites, in firewood piles and in stacks of bricks and stones. Little black ants feed on a wide variety of foods including live and dead insects, and the honeydew produced by aphids. The ants are active foragers and forage in trails of a few or up to hundreds of workers. These trails can be located along sidewalks and foundations and up the sides of buildings.

Drees, B. M., G. McIlveen, Jr., R. L. Crocker, C. Allen, M. Merchant and J. Reinert. 1993. Integrated pest management of Texas turfgrass. B-5083. Texas A&M University, College Station, Texas. 27 pp. Drees, B. M. 1997, 1998. House-Infesting Ants and Their Management. L-2061. Texas A&M University, College Station, Texas. 8 pp. (Reprinted 1/98) Drees, B. M. and J. A. Jackman. 1998. A Field Guide to Common Texas Insects. Gulf Publishers, Houston, Texas. 359 pp. Hodges, S. A.1992. Field Guide for the Management of Structure Infesting Ants. Pest Control Technology, Franzak & Foster Co. (4012 Bridge Ave., Cleveland, OH 44113) 155 pp.

Related Links:
L-2061, House-infesting Ants and Their Management
L-1783, Carpenter Ants
UC-033, Texas Leaf-cutting Ant
Factsheet #013, Texas Fire Ant Identification: An Illustrated Key [PDF]
Behavioral and Community Interaction of Phorid Flies and Fire Ants – University of Texas