Strumigenys rogeri

Strumigenys rogeri is a very small ant (total length ~ 2.5 mm) that nests in and under dead wood and preys on tiny soil arthropods. This species has spread to many parts of the world through human commerce. However, because S. rogeri workers are so small and slow moving, and they become motionless when disturbed, most people, including field biologists, remain unaware of their presence. Strumigenys rogeri apparently originated in tropical Africa, where its closest relatives all live, but it has become wide-spread on tropical islands of the Indo-Pacific and the West Indies, and in peninsular Florida. Outside of Africa and Florida, there are only a small number of continental records of S. rogeri, including a few from South and Central America and just one from continental Asia, in peninsular Malaysia. It is unclear whether S. rogeri has not yet spread to these continental areas, whether continental ants have competitively excluded S. rogeri, or whether these ants have been simply overlooked in surveys of diverse continental faunae. There is little information on what impact S. rogeri may be having on the native mesofauna in its exotic range. (Wetterer 2012)

Identification
See the description section below.

Bharti & Akbar (2013), India - The species is easily recognized in the Indian fauna as it is the only one to have the ventrolateral margin of the head deeply indented immediately in front of the eye, so deeply that the anterior portion of the eye is detached from the side of the head. Ventral surface of head with a transverse preocular im¬pression that is posterior to and separate from the postbuccal groove. Preapical dentition of each mandible of two articles; with a preapical tooth and a denticle (Bolton, 2000).

Distribution
In Florida (where it is introduced) it is a common species in bayheads and swamp forest as far north as northern Orange County. Pest status: none. First published Florida record: Deyrup and Trager 1984; earlier specimens: 1965. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Burundi, Cameroun, Comoros, Gabon, Ghana, Ivory Coast, Nigeria, United Republic of Tanzania. Australasian Region: New Caledonia. Indo-Australian Region: Borneo, Fiji, Indonesia, Malaysia, Marshall Islands, Micronesia (Federated States of), New Guinea, Niue, Northern Mariana Islands, Philippines, Samoa, Solomon Islands, Tonga, Vanuatu, Wallis and Futuna Islands. Malagasy Region: Madagascar, Mauritius, Mayotte, Réunion, Seychelles. Nearctic Region: Canada, United States. Neotropical Region: Barbados, British Virgin Islands, Costa Rica, Cuba, Dominican Republic, Greater Antilles, Haiti, Honduras, Lesser Antilles, Mexico, Puerto Rico, Saint Lucia. Oriental Region: India. Palaearctic Region: United Kingdom of Great Britain and Northern Ireland.





Biology
Brown (1954):

"I am fortunate also in having important notes on the biology of S. rogeri made by E. O. Wilson during his stay in Cuba in the summer of 1953.

Wilson took his observation colony at San Vicente, Pinar del Rio, Cuba, from a small nest under a rotten limb lying on well shaded ground. The galleries extended into the wood itself. Transferred to a small plaster observation nest, the workers readily captured numbers of entomobryoid collembolans proffered; campodeids up to four times the length of the ants were also always accepted and, like the entomobryoids, were fed to the larvae. Also observed to be chewed by the larvae after capture were a small psocopteran, a small ichneumonid wasp, and a small, injured embiopteran that had previously been ignored by a colony of Smithistruma nigrescens (= Strumigenys nigrescens) Wheeler. A symphylan and a pseudoscorpion, one each, were accepted and eaten by the larvae, but only after lengthy contact with the ants. Other specimens of these last two groups seem to have been refused by the larvae after capture on some occasions. A small polydesmid millipede was also captured, but soon rejected by larvae and workers. Consistently avoided or ignored when offered in the intimate confines of the observation nest were mites, nasute and other termites, small isopods, poduroid collembolans, adult staphylinid and sylvanid beetles of small size, a small campodeiform beetle larva, and dead mosquitoes, though the beetles mentioned disappeared from the nest and may possibly have been eaten.. Drosophila adults werc caught by the adults, but later discarded.

Entomobryoid collembolans seemed to be the usual and preferred prey fed to the larvae, although campodeids were never refused. In feeding habits, therefore, S. rogeri follows the generic habit of collembolan predation but, like some other widespread dacetine species, it will also accept a variety of other small arthropods, particularly campodeids, when available. In hunting, or when disturbed, the workers and females open the mandibles to slightly more than 180 degrees."

Florida (USA)
Deyrup (1997) reports this species is often the dominant dacetine ant in moist hammocks and swamp forest.

Clouse (1999) - Found Strumigenys rogeri to be common in wet areas of Everglades National Park and occurring in high densities along marshy trails on the Eastern Florida coast.

Deyrup, Davis & Cover (2000): This species is the common dacetine in bayheads, baygalls, and other swamp forest habitats in south and central Florida. Samples collected by Walter Suter between 1960 and 1970 suggest that several species of Strumigenys, including Strumigenys louisianae, were much more common in the absence of S. rogeri than they are today, although our survey methods may not replicate Suter's, and there have been many other changes in Florida since 1970. Since this species is apparently moving northward, it might be useful to do some intensive sampling ahead of its advance.

Puerto Rico
Wheeler (1908): Numerous workers and females taken from several colonies nesting under stones in a nearly dry stream bottom behind the Coamo baths. The rediscovery of the female of this species shows that Emery was right in his contention that Roger had described two very different species under the name of Pyrmaica gundlachi (=Strumigenys gundlachi). The females among my specimens agree perfectly with Roger's description and figure (Taf. I, .Fig. 18a).

Nomenclature

 *  rogeri. Strumigenys rogeri Emery, 1890b: 68, pl. 7, fig. 6 (w.) ANTILLES. Forel, 1893g: 378 (q.). Senior synonym of incisa: Donisthorpe, 1915d: 341; of sulfurea: Brown, 1954k: 20. See also: Bolton, 1983: 387; Bolton, 2000: 604.
 * incisa. Strumigenys incisa Godfrey, 1907: 102 (w.) GREAT BRITAIN. Junior synonym of rogeri: Donisthorpe, 1915d: 341.
 * sulfurea. Strumigenys sulfurea Santschi, 1915c: 261 (w.) GABON. Junior synonym of rogeri: Brown, 1954k: 20.

Worker
Bolton (2000) - TL 2.3 - 2.8, HL 0.58 - 0 .74, HW 0.42 - 0.52, CI 69 - 75, ML 0.30 - 0.40, MI 51 - 58, SL 0.36 - 0.46, SI 82 - 89, PW 0.27 - 0.32, AL 0.56 - 0.68 (45 measured). Characters of rogeri-complex''. Mandibles relatively stout and more or less straight through most of their length; not obviously bowed outwards. On each mandible proximal preapical tooth stout and usually no longer than maximum width of mandible, usually slightly shorter. Distal preapical tooth shorter than proximal but nearly as stout. On right mandible distal preapical tooth slightly longer and thicker than on left mandible; not completely concealed by left apicodorsal tooth at full closure.

Type Material
Bolton (2000):

Holotype worker, ST THOMAS I. (West Indies) [examined].

Strumigenys incisa Godfrey, 1907: 102 [attributed to Forel]. Syntype workers, GREAT BRITAIN: Scotland, Edinburgh, hothouse in Royal Botanic Garden, 10.vi.1904 (R. Godfrey) [examined].

Strumigenys sulfurea Santschi, 1915: 261. Syntype workers, GABON: Samkita (F. Faure) [examined].