European fire ant workers (Myrmica rubra L.) are approximately 5mm (3/16”) long and range in color from orange to dark reddish-brown. See the illustration to the left for more identifying characteristics. European fire ants do not build mounds; rather, they usually nest inside logs or in the soil under stones and other debris. Nest density is typically very high in infested areas and workers are quite aggressive.
European fire ants are native to Europe and central Asia. They are generally not considered to be pests in their native range.
Invasion history and invasive range:
European fire ants have been found many times in shipments of plant material from several European countries. The exact origin of the ants currently established in North America is not known. European fire ants have been a problem in some Maine communities for over 50 years; however, it is over the last 15 years that they have become widespread. There are currently infestations in many communities along the entire
Maine coast as well as several inland sites and areas of other northeastern states and Maritime Provinces.
The spread of invasive populations:
European fire ants in North America can have a density of 0.5 to 1.4 nests per square meter with 300 to 12,000 workers per nest. This is an order of magnitude greater than the density found in Europe. The fire ants are polygynous, meaning that they have multiple queens per nest. They spread through a process called colony budding, in which a queen and a small group of workers leave their mother nest on foot and start a satellite nest nearby.
The fire ants are also often spread through human activities. They nest in garden and landscaping materials, including potted plants, soil, compost, tree balls and mulch. Entire nests can be inadvertently transplanted along with these materials.