You’ve never seen this specific ant before, but it is probably like all the rest so you treat it like the others you’ve encountered in the past. Next week, the ants are still there. Could this be an ant introduced into your area? Should you have it identified? Have others observed this ant in your area? Does this ant occur in your backyard? Good observations! Good questions!
Ants seem like an unlikely pest to be moved from one part of the country to another or from one part of the world to another. After all, they are social insects and movement would require a mated queen with some supporting workers. So why have ghost ants been discovered in Edmonton, Alberta and Winnipeg, Manitoba? Why have white-footed ants been identified in Seattle, Wash.? Both of these ants usually occur in tropical or subtropical areas. These incidents, plus many others, illustrate that ants are moving around the globe through commerce or other means of transport.
WHAT CAN YOU DO? Pest management professionals (PMPs) are on the front lines of the industry and, therefore, will have the first opportunity to intercept these accidental introductions of tramp or exotic species of ants. When “new” ants appear in accounts, PMPs should collect and submit these ants for identification. Pest management professionals are familiar with most of the ant species in their area and new species should be reported.
So why are some ant species easily introduced into new areas? This occurs because of (1) the specific biology of the ant and (2) movement of people and commerce. Features of ant biology that provide for easy introductions include several factors. These colonies are usually polygynous, that is, the colonies have a number of queens and these colonies usually reproduce by budding. Many of these colonies are also polydomous, that is, they normally have a number of nesting sites and the colonies are very large. The increased mobility of people who are relocating and bringing their household belongings with them is introducing ants into new environments. Commerce is also responsible for movement of ants through the products themselves, through packing and crating materials, or cargo containers. With the introductions of atriums and indoor plantings, some ants that could not survive in an exterior setting because of cold weather may become established in shopping malls, housing complexes or hotels because of the constant warm temperatures.
PROPER ID = PROPER IPM. The importance of pest identification has long been recognized as an essential Integrated Pest Management tool. Some of these introduced species are well established, some are currently being introduced into new areas, so it’s critical any unfamiliar ant be properly identified.
Pharaoh ants have been established in most urban areas in both North America and Europe. This tropical ant, which probably originated in Africa, has been transported worldwide in commerce. This ant is well adapted to indoor environments where it could not survive on the exterior of buildings. This light-colored, small ant (1.5-2.0 mm) is usually best managed with commercial baits.
Other ants that may not be in your area but can be moved through commerce and movement of households include, but are not limited to, the following:
Ghost ants, Tapinoma melanocephalum, which originated in Asia or Africa are common in the Caribbean area, Florida and Hawaii and have made appearances in Seattle, Wash.; Portland, Ore.; and cities in Canada. These ants have been traced to packing materials and vegetation. The zoo in Portland, Ore., has been trying to manage these ants for more than 15 years. This small ant (2 mm) is easily recognized by the pale to white legs and gaster (abdomen), and the black head and mesosoma (thorax).
A ponerine ant, Hypoponera punctatissima, is another tropical ant, occurring in southern Florida, but also collected by pest management professionals in Vancouver, British Columbia; Prince Edward Island, Canada; and the states of Washington, Oregon, Connecticut and New York. These small (2 mm) ground-nesting ants live under concrete slabs and usually only the winged females emerge into structures. The females sting occupants and pose a health problem to people susceptible to the stings. The colonies are usually small and difficult to locate because of their location. Light traps may be effective in attracting the winged females.
The white-footed ant, Technomyrmex albipes, occurs in southern Florida, but also has been reported in states throughout the Southeastern U.S. and Hawaii. The ant also has been reported in California and Washington. This black ant is about 3 mm in length and is characterized by having white or pale yellow tarsi. The colony structure for this ant is unique in that about half the colony is composed of wingless males or females (intercastes) and the colonies are extremely large and spread over a number of sites, including areas inside and outside structures. Both baits and perimeter sprays are used in management, but the size of the colonies limits these treatments.
The crazy ant, Paratrechina longicornis, receives its name from its method of foraging. It runs very rapidly in a zigzag fashion. The ants are dark colored and about 3 mm in length with a hairy body. These ants originated in Asia or Africa and are common in the southeastern U.S. Through commerce they also have been reported in Arizona, New York, Ohio, Pennsylvania and California, as well as Toronto, Ontario. Nesting sites are varied and these ants can be found under lumber, stones, vegetation and mulch. Potted plants are common nesting sites either inside or outside.
The acrobat ant includes several species of Crematogaster that vary in size. All have a heart-shaped gaster that is held upright over the body, hence its descriptive name. These ants are found in North America and Europe. Specific examples of transport include travel trailers and foam blocks. Some of these species burrow in wood in landscaping and in wood and insulation within structures. These structurally damaging species may require treatments, including dusts in wall voids, in addition to perimeter sprays.
The term “fire ant” is associated with a number of species. Some of these are native species such as the Southern or California fire ant, Solenopsis xyloni, or the tropical fire ant, Solenopsis geminata, which occurs in the southern U.S. and are generally not considered to be tramp or exotic ants. The three ants discussed below also are called “fire ants” but these species have a high potential of being moved from one area to another.
The spread of the red imported fire ant, Solenopsis richteri, since its introduction from Brazil into the southeastern United States, has been observed moving north along the Atlantic coast and west to the Pacific. This ant (3.7-7 mm), with its painful sting, is an important health threat where it occurs. It displaces native species and may be confused with other native fire ants. Some biological controls are used; baits are important tools in management by pest management professionals.
The little fire ant, Wasmannia auropunctata, from Central and northern South America, is established in southern Florida. In addition, this ant has been introduced to Hawaii and isolated cases have occurred in California and Vancouver, British Columbia. The common name should not be confused with the red imported fire ant. This very small ant (1.5 mm) is reddish color and delivers a potent sting, which is a serious health threat. Colonies also cause serious problems to the eyes of pets (dogs and cats) when they sting as the animals feed.
The European fire ant, Myrmica rubra, occurs in Europe. This ant was introduced into North America in the early 1900s and is established in eastern Canada and northeastern U.S. These ants are yellowish brown and about 4 mm in length. Another species, M. incompleta, is found in western Canada, Alaska and northwestern states. These species normally live outside, but homeowners in both areas report stings by workers of these ants.
ALWAYS BE ON GUARD. This article includes only a few of the ants that are currently being identified in new areas around the world. As travel, commerce and relocation of people and households continue, new species will continue to be introduced. These ants may or may not become established. With the interior design of buildings and the constant heat provided in northern latitudes, many of these ants have the potential to become established. If infestations are identified early, management strategies can be implemented.
What can you do? Be observant. Ants that are not familiar to you should be collected and taken to someone who can identify the ant. Collect workers or foragers because winged forms are difficult or impossible to identify. Cooperative Extension offices of local counties and universities have people on staff to identify ants or send them to someone who can make positive identifications. You also have the resource of personnel at the National Pest Management Association or your state association. Also, authors of books and periodicals welcome your input and are often willing to help with identifications. This needs to be a cooperative venture. As PMPs you are on the forefront of the industry. You encounter these ants first and can become part of our cooperative approach to managing ant populations.
The author is a professor of biology at Spokane Falls Community College, Spokane, Wash.
References
Hedges, S. A. 1998. Field Guide for the Management of Structure-Infesting Ants. GIE Media, Cleveland, Ohio.
Klotz, J. 2004. Ants. Chapter 11. Mallis Handbook of Pest Control, 9th ed., GIE Media, Cleveland, Ohio.