Brachymyrmex

Mayr, 1868

Rover Ants

Brachymyrmex is a of minute in the Formicinae, commonly known as rover ants. are distinguished by having only nine antennal —fewer than most ants—and by the being concealed by the in view. The genus contains 44 and 17 , though species-level identification is challenging due to minimal morphological variation, small size, and soft-bodied workers. Brachymyrmex patagonicus, the dark rover ant, has become a significant pest in the southern United States and other regions worldwide.

Brachymyrmex patagonicus by (c) Sam Kieschnick, some rights reserved (CC BY), uploaded by Sam Kieschnick. Used under a CC-BY license.

Brachymyrmex by (c) Jake Nitta, some rights reserved (CC BY), uploaded by Jake Nitta. Used under a CC-BY license.

Pronunciation

How to pronounce Brachymyrmex: //ˌbræk.hɪˈmɜːr.mɛks//

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Identification

have nine antennal with no , distinguishing them from most which have more segments. The is concealed by the in view. Workers are minute (maximum 2.5 mm in B. patagonicus), with soft metasoma and simple that makes detailed observation difficult. The lacks the hairy legs and distinct antennal funiculus proportions that characterize some related .

Images

Habitat

range: naturally disturbed in South America, particularly Argentina and Paraguay. range: urban and residential environments, buildings, and structures; occurs in areas with specific vegetation , cover levels, and soil bulk . thrive in human-modified landscapes across the southern United States.

Distribution

: Neotropical region from United States to Argentina and Chile, including Caribbean islands; specifically Argentina and Paraguay for B. patagonicus. range: B. patagonicus to southern USA (first reported 1976, now 15 states from Georgia to California), Bahamas, continental Asia, Spain, Martinique; indoor occurrences in England, Netherlands, and Japan with uncertain outdoor survival. Some Brachymyrmex introduced to Japan and Madagascar.

Life Cycle

Nests are small and contain hundreds of . New and males are produced in nests. occurs primarily through rather than colony ; no isolation by distance suggests strong dispersal ability.

Behavior

B. patagonicus exhibits a multicolonial structure unusual for : each colony occupies a single nest with strong aggression toward non-nestmates, including biting and formic acid spraying that escalates to fighting with locked . Colony boundaries are maintained through nestmate recognition mediated by cuticular hydrocarbon chemical differentiation. Aggression levels between colonies correlate with genetic difference. Foraging trails from different colonies can occur in extremely close proximity (few centimeters) with mutual at trail level but aggression between individual . Workers do not bite or humans.

Ecological Role

B. patagonicus is an ecologically that reaches extremely dense (colonies every 2.5 meters in some areas). Unlike most that eliminate through supercolonial cooperation, this maintains high despite strong territorial aggression between colonies. Acts as a of : B. patagonicus has been observed subduing ().

Human Relevance

B. patagonicus is a significant nuisance pest infesting buildings in urban environments across its range. are small, do not bite or , and do not mechanically transmit . The has spread rapidly since its first in the United States in 1976, becoming established in 15 states.

Similar Taxa

Wasmannia auropunctata (little fire ant)Similar tiny size and coloration; distinguished by W. auropunctata's painful and different antennal segmentation.
Plagiolepis alluaudi (Alluaud's little yellow ant)Similar minute size (<2 mm), color, and status in urban environments; distinguished by P. alluaudi's extreme and unicolonial structure versus B. patagonicus's monogyne multicolonial organization.
Paratrechina longicornis, Pheidole megacephala, other tramp ant speciesShare global status and urban preference; distinguished by Brachymyrmex's unique nine-segmented and concealed .