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Subfamily MYRMICINAE
Tribe ATTINI
Strumigenys silvestrii Emery, 1906

Authors: Joe A. MacGown and Ryan J. Whitehouse
Uploaded, 2009; last updated 30 August 2016

Strumigenys  silvestrii, full face view of worker (MS, George Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, lateral view of worker (MS, George Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii,dorsal view of worker (MS, George Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, full face view of alate queen (MS, Clarke Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, lateral view of alate queen (MS, Clarke Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, dorsal view of alate queen (MS, Clarke Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, lateral view of alate queen (MS, Clarke Co.) (photo by Ryan Whitehouse and Joe A. MacGown)
Strumigenys  silvestrii, lateral view of mesosoma of worker (MS) (SEM photo by Joe A. MacGown and Richard Brown)
Strumigenys  silvestrii, close up view of a seta found on gastral dorsum of worker (MS) (SEM photo by Joe A. MacGown and Richard Brown)
Strumigenys  silvestrii, full face view of worker (MS) (SEM photo by Joe A. MacGown and Richard Brown)
Strumigenys  silvestrii, mandibles of worker (MS) (SEM photo by Joe A. MacGown and Richard Brown)
Strumigenys  silvestrii, clypeal area of worker(MS) (SEM photo by Joe A. MacGown and Richard Brown)

Introduction
Strumigenys is a monophyletic genus of dacetine ants that includes over 900 species worldwide (Bolton 2013). Forty-eight described species of Strumigenys have been reported from the US (Bolton 2013), but this genus is most speciose in the Southeast where at least 43 species are known to occur.

In the US, members of the genus Strumigenys can easily be distinguished from other genera by their minute size; 4-6 segmented antennae; elongate, snapping mandibles; unique and often "bizarre" pilosity, and presence of "spongiform lobes" beneath the petiole and postpetiole (Bolton 1999). Dacetines are predatory ants that generally feed on tiny soil arthropods (Wilson 1953).  Most dacetines are small, cryptically colored, rarely forage openly above ground, are slow moving, and become motionless when disturbed.

Strumigenys silvestrii is presumably a South American species that has been spreading around the world. Its food habits are probably similar to other exotic Strumigenys sp., but not too much is known about S. silvestrii specifically.

Taxonomic History
Strumigenys silvestrii Emery, 1906: 168, fig. 27 (w.q.) ARGENTINA. Neotropic.
Senior synonym of Strumigenys caribbea: Brown, 1959}: 25. See also: Bolton, 2000: 559.

Identification
Worker: HL 0.44-.046mm, HW 0.34-0.36mm, SL 0.30-0.32mm, EL 0.02-0.03mm, MeSL 0.44-0.47mm (n=5) (MEM specimens). This is a minute light-brown ant. Head is heart-shaped and densely punctate with anteriorly flexed scale-like setae; eyes are small and simple, only a few facets, located laterally below the antennae; mandibles long, approximately half the length of the head, with three distinct apical teeth; approximately half way down the inner margin of the mandible there is a small denticle; antennal scape nearly reaching occipital border, but not surpassing it; setae on the scape flexed anteriorly and posteriorly; antennae 6-segmented with the apical segment subequal in length to the scape. Mesosoma is densely punctate with a smooth meso- and metaplueral region; erect, scale-like setae present on the dorsal surface; dorsal surface forming a continuous arc in lateral view; the promesonotal suture forming a distinct carinae; propodeum distinctly armed with one tooth. Waist is 2-segmented; posteriorly flexed, erect setae present; spongiform tissue present on the ventral side of the postpetiole.  Gaster with robust, erect setae; smooth and shinning with longitudinal grooves originating dorsally from the base of the postpetiole.

Queen: HL 0.48mm, HW 0.38mm, SL 0.30mm, EL 0.07mm, MeSL 0.52mm (n=1) (MEM specimen). Minute brown ant, slightly darker than the workers and slightly longer. Head heart-shaped and densely punctate with erect, scale-like setae; eyes well-developed and large when compared with the worker, but still only about four facets wide; three ocelli present with some black pigmentation around them; mandibles long, approximately half the length of the head, with a distinct apical fork followed by a single tooth; approximately half way down the inner margin of the mandible there is a small denticle; antennal scape nearly reaching the occipital border; scape with anteriorly and posteriorly flexed setae; antennal scrobe with distinct dorsal and ventral edges along part of its length; antennae 6-segmented; apical antennal segment subeqaul in length to the scape. Mesosoma densely punctate with the meso- and metaplural region smooth; stout, erect setae present on the dorsal surface; enlarged with the presence of four wings or wing scars; propodeum distinctly armed with one tooth. Waist is 2-segmented; posteriorly flexed, erect setae present; spongiform tissue present on the ventral side of the postpetiole. Gaster smooth and shining with longitudinal grooves originating dorsally for the base of the postpetiole; erect setae present.
 
Biology and Economic Importance
Strumigenys silvestrii has been found in leaf litter in coastal hardwood forests, bottomland hardwood forests, the Black Belt Prairie, and vacant urban lots. Ants in this genus tend to be slow moving and very cryptic, often halting all movement when disturbed, as well as rarely venturing into the open. Strumigenys silvestrii most likely feeds on Collembola and other small soil arthropods with their trap-jaw mandibles, like other species in this genus with similar mandibles.

At the moment, the ecological and environmental effects of this species are not well known.

Distribution
Native Range: South America (AntWiki.org and MEM).

Nearctic: United States (AntWiki.org, MEM).
Neotropical: Argentina, Bahamas, Brazil, Cuba, Dominican Republic, Greater Antilles, Mexico, Paraguay (AntWeb.org and AntWiki.org).
Palearctic: China, Iberian Peninsula, Macaronesia, Portugal (AntWeb.org and AntWiki.org).

U.S. Distribution: AL, CA, FL, GA, LA, MS, TX (AntWiki.org and MEM).
Southeastern U.S. Distribution: AL, FL, GA, LA, MS (MEM).

Literature Cited
Bolton, B.  1999.  Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae).  Journal of Natural History 33: 1639-1689.

Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65:1-1028.

Bolton, B. 2013.  Bolton World Catalog Ants. Available online: http://www.antweb.org/world.jsp. Accessed 16 April 2013.

Brown, W. L., Jr. 1959. The neotropical species of the ant genus Strumigenys Fr. Smith: group of silvestrii Emery. Studia Entomologica (n.s.) 2:25-30.

Emery, C. 1906 ("1905"). Studi sulle formiche della fauna neotropica. XXVI. Bullettino della Società Entomologica Italiana 37:107-194.

Wilson, E. O. 1953. The ecology of some North American dacetine ants. Annals of the Entomological Society of America 46: 479-497.

Links
AntCat
AntWeb
AntWiki