Crematogaster sotobosque

Nests with brood and sexuals have never been found but aggregations of workers, in carton shelters in leaf litter, suggest they are not arboreal.

Identification
Longino (2003) - The combination of smooth and highly polished body surface, amber dorsal setae, and suberect tibial pilosity uniquely identifies this species. In some ways it is like a small version of Crematogaster nigropilosa, with smaller propodeal spines.

Distribution
Costa Rica to Amazonian Brazil and Peru.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Colombia, Costa Rica, Ecuador, Panama, Peru, Venezuela.

Biology
Longino (2003) - Crematogaster sotobosque occurs in lowland and mid-montane mature wet forest habitats. Workers are frequently collected in Winkler samples of sifted leaf litter from the forest floor, and dealate queens are occasionally encountered as well. Workers forage on low vegetation in the forest understory. I usually find foragers at night, but have also seen them during the day in heavily shaded forest. Foragers are solitary and usually very thinly dispersed over the vegetation. I have attracted workers to sugar baits and to dead mosquitoes, but I never see large aggregations of foragers.

Although observations are few, nests appear to be diffusely spread in the forest leaf litter. In one case I baited a worker with a dead mosquito and followed it back to a small carton shelter in the leaf litter around the base of a fern. The shelter contained only workers, with no brood or sexuals, but a search of the surrounding litter yielded a lone queen with a packet of brood in a hollow stick. There were no workers with her, but she was only a few centimeters from the carton shelter. On other occasions I have found aggregations of workers in small shelters in the leaf litter, between dead leaves, with small amounts of carton construction, but have been unable to find any chambers with brood or sexuals in the vicinity. These observations of broodless worker bivouacs is tantalizing and suggests an interesting nesting and foraging behavior.

Nomenclature

 *  sotobosque. Crematogaster sotobosque Longino, 2003a: 106, pls. 1, 5 (w.q.) COSTA RICA.

Worker
Holotype: HL 0.519, HW 0.565, HC 0.508, SL 0.557, EL 0.145, WL 0.639, SPL 0.182, PTH 0.152, PTL 0.250, PTW 0.145, PPL 0.175, PPW 0.162, CI 109, OI 28, SI 107, PTHI 61, PTWI 58, PPI 93, SPI 28. Other specimens: HL 0.466, 0.466, 0.549; HW 0.514, 0.501, 0.595; HC 0.459, 0.452, 0.525; SL 0.507, 0.532, 0.584; EL 0.128, 0.130, 0.135; A11L 0.239; A11W 0.111; A10L 0.132; A10W 0.081; A09L 0.054; A09W 0.064; A08L 0.038; A08W 0.045; WL 0.571, 0.560, 0.660; SPL 0.128, 0.121, 0.147; PTH 0.128, 0.134, 0.154; PTL 0.207, 0.196, 0.255; PTW 0.123, 0.126, 0.146; PPL 0.138, 0.148, 0.168; PPW 0.142, 0.125, 0.157; CI 110, 108, 108; OI 27, 28, 25; SI 109, 114, 106; PTHI 62, 68, 61; PTWI 60, 64, 57; PPI 103, 84, 93; SPI 22, 22, 22; ACI 1.07.

Color brown with contrasting yellow mandibles and antennal club, legs lighter than body but not as yellow as mandibles and club.

Mandible smooth and shiny; anterior margin of clypeus weakly convex; clypeus convex, smooth and shiny; face smooth and shiny; scapes with abundant long erect setae of variable lengths, many setae much longer than scape width; terminal three segments of antenna differentiated, larger than preceding segments, terminal two segments largest and most conspicuous, appearing as two-segmented club; face with abundant medium length erect dark setae; in full face view a row of dark erect setae project from posterior margin of head, fine short curved setae project from sides of head anterior to eyes.

In lateral profile pronotum rises from anterior collar to flat-topped promesonotal dorsum, then drops steeply to propodeal suture; no trace of promesonotal suture; juncture of dorsal and posterior face of promesonotum with pair of projecting tubercles, formed from apices of pair of strong carinae on posterior face, carinae converging posteriorly and continuing across propodeal suture; dorsal and posterior faces of propodeum not differentiated, sloping continuously from propodeal suture to petiolar insertion; propodeal spines broad based, medium length, tapering to long acute tips, slightly curving upward; entire mesosoma smooth and shining, with no other sculptural elements besides pair of carinae on posterior mesonotum; promesonotal dorsum with three pairs of setae, one on humeri, one midlength, and one on mesonotal tubercles, progressively shorter from anterior to posterior, with very long humeral setae and relatively short setae on mesonotal tubercles; setae dark; one or two dark setae on each propodeal spine; legs with suberect pubescence and scattered long erect setae.

Petiole in side view trapezoidal, smooth and shiny; anteroventral tooth small but usually distinct, forming a rounded angle; dorsal face elongate, tapering anteriorly, smooth and shiny, with a single long dark seta on each posterolateral corner; postpetiole with no ventral tooth, in dorsal view globular, widest posteriorly and tapering anteriorly, well separated from petiole by anterior peduncle, with two pairs of long dark setae; fourth abdominal tergite smooth and shining, with sparse, very long erect dark setae.

Queen
A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum); mandibles smooth and shiny; clypeus smooth and shiny; scape with abundant suberect setae; antennal club as in worker; abundant long erect setae on face, ventral surface of head; in full face view abundant curved setae projecting from posterior and lateral margins of head, both posterior and anterior to eye; large, conspicuous ocellate puncta moderately abundant on face, very abundant on mesonotum and scutellum, sparse on side of pronotum, anepisternum, and katepisternum, interspaces smooth and shining; abundant medium-length flexuous erect setae on mesonotum and scutellum, sparser but conspicuously present on side of pronotum, anepisternum, and katepisternum; propodeum coarsely rugose, rugae generally longitudinally oriented, becoming effaced on oval region above petiolar insertion; propodeal spines long, narrowly acute, spiniform; propodeal spiracle very large; sides of propodeum and propodeal spines with abundant erect setae; legs with abundant suberect setae, on both femora and tibiae; petiole shape as in worker but more robust, relatively shorter and wider in dorsal view, sides faintly punctate, dorsal face with abundant setae along posterior margin; postpetiole without ventral tooth, in dorsal view subquadrate to globular, widest anteriorly, with abundant erect setae; fourth abdominal tergite smooth and shiny with abundant long erect setae; size characters as in Figures.

Type Material
Holotype worker. Costa Rica, Prov. Heredia, La Selva Biological Station, 10°26'N, 84°01'W, 50m, 23 Oct 1991 (Longino, collection code JTL3136-s), specimen code INBIOCRI001237410.

Paratypes. One queen, same data as holotype and on same pin INBC, specimen code INBIOCRI001237410; one worker and one queen on same pin, same data, specimen code INBIOCRI001218088; two workers, same locality, 17 Jul 1986 (Longino, collection code JTL1391-s) , specimen code JTLC000001217; one worker, same locality, 25-29 Jun 1999 (INBio-OET, Project ALAS collection code W/14/013) , specimen code INBIOCRI002720738; one worker, same data , specimen code INBIOCRI002720739; one worker, same data , specimen code INBIOCRI002720740; one worker, same data , specimen code INBIOCRI002720741; one worker, same data , specimen code INBIOCRI002720742.

Etymology
This species is named after the Spanish word for forest understory, reflecting its favored habitat.

Determination Clarifications
Crematogaster JTL-006: Longino et al. 2002.

References based on Global Ant Biodiversity Informatics

 * Fernandes I., and J. de Souza. 2018. Dataset of long-term monitoring of ground-dwelling ants (Hymenoptera: Formicidae) in the influence areas of a hydroelectric power plant on the Madeira River in the Amazon Basin. Biodiversity Data Journal 6: e24375.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Fichaux M., B. Bechade, J. Donald, A. Weyna, J. H. C. Delabie, J. Murienne, C. Baraloto, and J. Orivel. 2019. Habitats shape taxonomic and functional composition of Neotropical ant assemblages. Oecologia 189(2): 501-513.
 * Franco W., N. Ladino, J. H. C. Delabie, A. Dejean, J. Orivel, M. Fichaux, S. Groc, M. Leponce, and R. M. Feitosa. 2019. First checklist of the ants (Hymenoptera: Formicidae) of French Guiana. Zootaxa 4674(5): 509-543.
 * Groc S., J. H. C. Delabie, F. Fernandez, M. Leponce, J. Orivel, R. Silvestre, Heraldo L. Vasconcelos, and A. Dejean. 2013. Leaf-litter ant communities (Hymenoptera: Formicidae) in a pristine Guianese rainforest: stable functional structure versus high species turnover. Myrmecological News 19: 43-51.
 * Groc S., J. Orivel, A. Dejean, J. Martin, M. Etienne, B. Corbara, and J. H. C. Delabie. 2009. Baseline study of the leaf-litter ant fauna in a French Guianese forest. Insect Conservation and Diversity 2: 183-193.
 * INBio Collection (via Gbif)
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Longino J. T., and R. K. Colwell. 2011. Density compensation, species composition, and richness of ants on a neotropical elevational gradient. Ecosphere 2(3): 16pp.
 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
 * Longino, J.T. 2003. The Crematogaster (Hymenoptera, Formicidae, Myrmicinae) of Costa Rica. Zootaxa 151:1-150
 * Lopes M. C., G. P. A. Lamarre, C. Baraloto, P. V. A. Fine, A. Vincentini, and F. B. Baccaro. 2019. The Amazonas-trap: a new method for sampling plant-inhabiting arthropod communities in tropical forest understory. Entomologia Experimentalis et Applicata https://doi.org/10.1111/eea.12797
 * Morgan C., and W. P. Mackay. 2017. The North America acrobat ants of the hyperdiverse genus Crematogaster. Mauritius: LAP LAMBERT Academic Publishing, 540 pp.
 * Morgan C.E., MacKay W.P. and Dash S.T. 2011. Discovery of the Neotropical Ant Crematogaster sotobosque (Hymentoptera: Formicidae) Near Tucson, Arizona. The Southwestern Naturalist. 53: 432-433
 * Sosa-Calvo J. 2007. Ants of the leaf litter of two plateaus in Eastern Suriname. In Alonso, L.E. and J.H. Mol (eds.). 2007. A rapid biological assessment of the Lely and Nassau plateaus, Suriname (with additional information on the Brownsberg Plateau). RAP Bulletin of Biological Assessment 43. Conservation International, Arlington, VA, USA.