ID guide | introduced ants

Ooceraea biroi

General description: 

Ooceraea biroi is a small (2–3 mm), brown, blind subterranean ant with short antennal scapes, a distinctly two-segmented waist, a powerful sting, and a cylindrical body armored with thick cuticle. The species is very inconspicuous owing to its hypogaeic foraging, and is rarely collected. It believed to be native to Asia (Brown, 1975; Wetterer et al., 2012), where it is widely spread from Nepal, India and China to South East Asia, and has established introduced populations throughout the Pacific Islands (where it was referred to by its junior synonym O. silvestrii) and the West Indies. Outside Asia, all records of O. biroi come from islands, possibly due to reduced competition with dominant ants in island habitats (Wetterer et al., 2012). It is also the only known species within the Cerapachyinae to successfully establish populations outside its native range. The introduced populations are not known to have any adverse impacts on agricultural systems or human health. The general biology and worldwide distribution was profiled by Wetterer et al. (2012). 


Like many of its congeners, O. biroi maintains colonies of up to several hundred workers that raid the brood of other ant species for food (Tsuji & Yamauchi, 1995), but will occasionally take the soft-bodied larvae of other insects (Wolcott, 1951 (1948)). The heavily sclerotized cuticle provides excellent protection against injury and dismemberment during prey raids, and the venomous sting is used to immobilize opponents (Hölldobler, 1982). The species alternates stationary and nomadic phases that are synchronized with the production of distinct brood cohorts (Ravary et al., 2006; Ravary & Jaisson, 2002). Ooceraea biroi belongs to a very small number of ant species known to reproduce through thelytokous parthenogenesis (Heinze, 2008; Ravary & Jaisson, 2004; Tsuji & Yamauchi, 1995). It has been proposed that this ability of workers to produce diploid eggs has facilitated the ability of O. biroi to establish new populations across the world (Yamauchi & Ogata, 1995). The ability of researchers to maintain colonies of O. biroi in laboratory settings (Ravary et al., 2007)also hint at its capacity as a successful tramp species. 

Diagnostic description: 

Diagnosis of worker among Antkey species. Antenna 9-segmented. Antennal insertions entirely exposed, not covered even partially by frontal lobes. Antennal scapes conspicuously short; barely surpassing eye level. Eyes minute to absent (equal to or less than 3 facets). Waist 2-segmented. Petiole narrowly attached to gaster and with conspicuous posterior face. Gaster armed with sting. Pygidium flattened and armed with a row of small peg-like teeth. Body cylindrically shaped. 

Ooceraea biroi is distinguished from all other introduced ants by the following characters: (1) waist with two segments; (2) eyes absent or reduced to a single ommatidia; (3) antennal insertions entirely exposed, not covered even partially by frontal lobes; (4) antennal scapes conspicuously short and barely surpassing eye level; (5) pygidium flattened and armed with a row of small peg-like teeth.


Native range. Widely spread through Asia, from Nepal, India and China to South East Asia.

Introduced range: Pacific Islands and West Indies.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith