Pheidole obscurithorax

Naves, 1985

Large Imported Big-headed Ant

Pheidole obscurithorax is a large, dark, to northern Argentina and Paraguay. It was to Mobile, Alabama in the early 1950s and has since spread along an 80-km-wide coastal between Alabama and Tallahassee, Florida. The is characterized by with enlarged-headed majors and has demonstrated rapid growth in invaded areas, with nest increasing 6.4-fold over two years in Tallahassee. It coexists with the () and appears to have minimal negative impact on native ant , being part of a largely ant adapted to disturbed .

Pheidole obscurithorax by (c) Tyler Bishop, some rights reserved (CC BY), uploaded by Tyler Bishop. Used under a CC-BY license.

Pheidole obscurithorax casent0104418 dorsal 2 by April Nobile. Used under a CC BY 4.0 license.

Pheidole obscurithorax casent0178042 label 1 by Michele Esposito. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Pheidole obscurithorax: //faɪˈdoʊli ɒbˌskjʊrɪˈθɔːræks//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are , with major workers possessing disproportionately large compared to . The is notably large and dark in coloration, reaching up to 6 mm in length. Major workers use their enlarged heads and for defense and processing. Nests are conspicuous, with single large openings 1-5 cm wide in soil, often covered by collected leaf material. Distinguished from other Pheidole species by its large size, dark coloration, and association with open, disturbed in the southeastern United States.

Images

Habitat

Open areas in disturbed , particularly roadsides with shorter grass. In its range, it occupies mature floodplain and open pasture in the Parana River region of northern Argentina and Paraguay. In the range, nest is highest near Pensacola, Florida.

Distribution

to northern Argentina and Paraguay. to the southeastern United States, where it currently occupies an 80-km-wide coastal between Mobile, Alabama and Tallahassee, Florida. First observed in Mobile, Alabama in the early 1950s; first observed in Tallahassee, Florida in 1998. The range is gradually expanding through natural . GBIF records indicate presence in multiple Brazilian states (Bahia, Maranhão, Minas Gerais, Mato Grosso do Sul, Mato Grosso, Pernambuco, Piauí, Rio Grande do Sul, São Paulo) and the conterminous United States.

Seasonality

Mating occur before dawn after summer rains.

Diet

. Collects a variety of including other —notably body parts have been found in nest middens. material such as flower petals is consumed less frequently. Uses team transport for large prey items. In urban environments, has been observed to play a role in food waste and removal.

Life Cycle

Colonies contain a single found up to 3 meters below the surface. Small mating observed before dawn after summer rains. Colony excavations reveal single queen per colony.

Behavior

exhibit combined foraging tactics: scouts carry small unaided while teams transport large prey whole. Defends prey items from other including , with mixed success in battles. Remarkable speed and size of prey handling has been observed. Produces conspicuous soil nests with single large opening often covered by collected material.

Ecological Role

Appears to have little negative effect on it invades. Coexists with . Part of a largely ant community tolerant of highly disturbed . Associated with lower expected at occupied sites (8 versus 16 at equivalent sampling), though this may reflect habitat preference for disturbed areas rather than competitive exclusion. Eight woodland ant species are absent from sites where P. obscurithorax is present. In urban environments, provides services through food waste and removal.

Human Relevance

Recognized as a in detecting and removing food waste in urban areas, contributing to services in densely populated environments. Considered a tramp species spread by human activity. Not regarded as a major compared to other ants, with minimal documented negative economic or ecological impact.

Similar Taxa

Pheidole megacephalaBoth are large, Pheidole with enlarged-headed major . P. megacephala is distinguished by its global distribution as one of the world's worst species, broader thermal , and more severe ecological impacts. P. obscurithorax is larger and darker, with a more restricted range in the southeastern United States.
Solenopsis invictaCo-occurs with P. obscurithorax in the southeastern United States. Both are , soil-nesting in disturbed . Distinguished by in S. invicta versus workers in P. obscurithorax, and by the apparatus present in fire ants.