Strumigenys hexamera is a small predatory ant that feeds on minute soil arthropods. Originally from East Asia, P. hexamera has been recently introduced to North America, apparently through human commerce. It is rare in Hong Kong with only two records, both from secondary forests at elevations of 142 and 160 m (Tang et al., 2019). It seems to have small monogynous colonies of about 35 individuals (Terayama et al. 2014).
- 1 Identification
- 2 Distribution
- 3 Biology
- 4 Castes
- 5 Nomenclature
- 6 References
A member of the argiola complex in the Strumigenys argiola group. Strumigenys hexamera is a minute (~2.0 mm in total length), brown species with elongate mandibles; in full face view only 3 teeth are visible, 2 preapical teeth and one very long apicodorsal tooth which extends over the tooth on the opposite mandible and beyond the outer margin of the opposite mandible. The entire head, scape, and even the mandibles are covered with large circular shaped, somewhat translucent setae. Spongiform tissue present beneath the petiole and postpetiole.
Within the United States, the unique mandibular structure and scale-like setae on the head and body will separate S. hexamera from other members of the genus.
Keys including this Species
- Key to Nearctic Strumigenys (as Pyramica)
- Key to Strumigenys of China (as Pyramica)
- Key to Strumigenys of East Asia (as Pyramica)
- Key to US Strumigenys species
A rare, introduced species known from two sites in central Florida. The sites were in mesic forest. This is our only known example of an ant apparently introduced into Florida from Japan. Pest status: none. First published Florida record: Deyrup 1988; earlier specimens: 1987. (Deyrup, Davis & Cover, 2000.)
Strumigenys hexamera is now well established in the southeastern US, especially in Mississippi where we have collected it throughout the state in over 17 counties. Compared to other alien species, S. hexamera appears to do well in natural wooded habitats. Joe MacGown has typically collected this species in rich mesic hardwood or mixed pine hardwood forests, often in areas with hilly terrain.
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
Strumigenys hexamera is subterranean, rather than living in leaf litter. It is a specialized ambush predator of small long-bodied soil arthropods, such as Diplura, Chilopoda, and Collembola (Masuko 1984). Masuko (2009) reported that “Diplura composed 60% of the prey in the field material.” This prey preference is unusual compared with most dacetines whose biologies have been studied, and which apparently prey primarily on Collembola (Masuko 2009). Foraging S. hexamera workers hunt for their prey in small crevices in the soil. Upon encountering prey, S. hexamera moves to a crouching position, pulls its antennae back into recessed antennal scrobes lining the side of the head, closes its mandibles, and remains motionless. The ant may remain still for >20 min while it waits for the prey to advance and crawl on top of her head. Strumigenys hexamera is uniquely equipped for this situation, having a flattened head and slightly upturned mandibles, each of which terminates with a sharp apical tooth, allowing the ant to strike at prey passing overhead. When the prey is in the correct position, the ant opens its mandibles and suddenly snaps them shut, impaling the prey with the apical teeth (Masuko 1984). Strumigenys hexamera has also been reported to coat its body with soil and other detritus using its forelegs, a behavior that may camouflage the ant's odor from the prey (Masuko 1984, see Strumigenys behavior).
Tang et al. (2019): The record of S. hexamera in Hong Kong represents the first record of this species for continental China. This species is known as an introduced species in Southeast USA (Alabama, Florida, Louisiana, and Mississippi), and was reported as introduced within the Ogasawara Islands (Shindo 1979). Here we tentatively classify this species as introduced to Hong Kong in light of its tramp characteristics, including its known thelytokous reproductive strategy (Masuko 2013), and the lack of previous collections in Hong Kong or other parts of mainland China. However, for this species, as for many tramp species across Asia, further study is needed to determine their exact origin and the extent of their native range. Malaise traps yielded female alates in sampling conducted from March 16 - March 31.
Also see Hunting Tactics in Short-Mandibulate Strumigenys for more about this ant's hunting behavior.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- hexamera. Epitritus hexamerus Brown, 1958d: 70, figs. 1-3 (w.q.) JAPAN. Combination in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 121. See also: Bolton, 2000: 388.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (2000) - TL 2.0-2.2, HL 0.50-0.53, HW 0.53-0.55, CI 106-108, ML 0.18-0.22, MI 36-42, SL 0.23-0.25, SI 46-47, PW 0.28-0.31, AL 0.57-0.60 (3 measured).
Apicodorsal tooth of mandible elongate and spiniform. Mandible with 2 preapical teeth, both located in distal half of mandible and the proximal preapical tooth somewhat longer than the distal. Dorsal surfaces of mandibles and scapes with orbicular hairs. Hairs on leading edge of scape curved toward apex of scape. Cephalic dorsum with orbicular hairs more or less evenly distributed; there is no hairless patch on each side mesad of the lateral margin in the area where the margins are most strongly divergent. CI > 100. Mesonotum in profile bulging posteriorly over base of propodeum, overhanging metanotal groove.
TL 2.8, HL 0.60, ML 0.20, WL 0.76, scape L 0.27, funiculus L 0.49 mm. CI 102, MI 34. Eyes moderate in size, well underneath on dorsal scrobe borders. Alitrunk robust, humeri very weakly subangulate, without tubercles. Mesonotum gently convex; scutellum rounded behind and not strongly projecting. Propodeal teeth extremely small, with infradental lamellae. Parapsidal furrows fine but distinct. Petiolar node shorter and broader than in worker, the anterior face more concave and the two carinae more distinct, forming a miniature peak on each side above. Mesonotum with orbicular squamiform hairs like those of head. As in the worker, there are no erect specialized hairs on head or alitrunk.
Bolton (2000) - Holotype worker and paratype worker, JAPAN: Kyushu, Provo Chikugo, Korasan, 25.ix.1955 (S. Miyamoto); paratype queen (dealate), JAPAN: Honshu, Numazu City, Sige-toge, 22.v.1949, 250 m., under stone (K. Okano) (Museum of Comparative Zoology) [examined].
Brown (1958) reported the head of the paratype queen has been lost.
- Baroni Urbani, C.; De Andrade, M. L. 1994. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe (Amber Collection Stuttgart: Hymenoptera, Formicidae. VI: Dacetini). Stuttg. Beitr. Naturkd. Ser. B ( (page 13, combination in Strumigenys)
- Baroni Urbani, C. and de Andrade, M.L. 2007. The ant tribe Dacetini: limits and constituent genera, with descriptions of new species. Annali del Museo Civico di Storia Naturale “G. Doria”. 99:1-191.
- Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). J. Nat. Hist. 3 33: 1639-1689 (page 1672, Combination in Pyramica)
- Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 388, redescription of worker)
- Brown, W. L., Jr. 1958d. A new Japanese species of the dacetine ant genus Epitritus. Mushi 31:69-72. PDF (page 70, figs. 1-3 worker, queen described)
- Deyrup, M., Davis, L. & Cover, S. 2000. Exotic ants in Florida. Transactions of the American Entomological Society 126, 293-325.
- Masuko, K. 1984. Studies on the predatory biology of oriental dacetine ants (Hymenoptera: Formicidae). I. Some Japanese species of Strumigenys, Pentastruma, and Epitritus, and a Malaysian Labidogenys, with special reference to hunting tactics in short-mandibulate forms. Insectes Sociaux. 31(4):429-451. doi:10.1007/BF02223658
- Masuko, K. 2009. Studies on the predatory biology of Oriental dacetine ants (Hymenoptera: Formicidae). III. Predation on gamasid mites by Pyramica mazu with a supplementary note on P. hexamerus. Journal of the Kansas Entomological Society 82: 109-113.
- Tang, K.L., Pierce, M.P., Guénard, B. 2019. Review of the genus Strumigenys (Hymenoptera, Formicidae, Myrmicinae) in Hong Kong with the description of three new species and the addition of five native and four introduced species records. ZooKeys 831: 1–48 (DOI 10.3897/zookeys.831.31515).
- Terayama, M., Kubota, S., Eguchi, K. 2014. Encyclopedia of Japanese Ants. Asakura Shoten: Tokyo, 278 pp.
- Terayama, M.; Lin, C.-C.; Wu, W.-J. 1995. The ant genera Epitritus and Kyidris from Taiwan (Hymenoptera: Formicidae). Proc. Jpn. Soc. Syst. Zool. 53: 85-89 (page 87, see also)
- Wilson, E. O. 1953. The ecology of some North American dacetine ants. Annals of the Entomological Society of America 46: 479-497.