Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Additional images: Worker, maxillary palpus (large); dorsal view (small) (large). Male, face view (large); wings (large); abdomen, side view (large), genitalia (large).
Nicaragua, Costa Rica, Colombia, Venezuela, Peru. In Costa Rica it occurs throughout the country above 500m elevation.
Diagnosis: Worker black; antenna 10-segmented; face sericeous or shagreened, not shining.
Worker: Antenna 10-segmented; maxillary palpus 6-segmented; mandible smooth to feebly rugose; clypeus somewhat roughened; most of face with fine striate microsculpture giving a silky luster, grading to smooth and shiny on vertex margin; sides, rear margin and ventral surface of head with sparse, short, appressed pubescence, no erect setae; scapes with abundant suberect setae, longer setae about 1/2 scape width; hind tibia with abundant subdecumbent setae, longer setae about 1/4 width of tibia; mesosoma strongly constricted at metanotal groove, hourglass-shaped; entire mesosoma with reticulate microsculpture, matte; petiole in side view with compressed, scale-like node; color solid black. Also see description of Emery (1896).
Measurements: HL 0.521-0.720, HW 0.506-0.708, SL 0.364-0.472, EL 0.113-0.169, CI 92-100 (n=5).
Queen (previously unknown): Similar to worker in meristic characters, patterns of sculpture, pilosity, coloration. Labrum short, bilobed.
Measurements: HL 0.904-1.031, HW 0.836-0.939, SL 0.465-0.534, EL 0.267-0.323, OW 0.061-0.080, OD 0.206-0.237, CI 90-92, OI 32-35, OcI 7-8 (n=5).
Male: See description of Wheeler (1934). Antenna 11-segmented; maxillary palpus 6-segmented; pygostyles present, sclerotized, setose; basiparamere lobe and paramere short, robust, broadly triangular; cuspis robust, spatulate, with an apicodorsal field of small teeth at the apical contact point with the digitus; digitus short, dorsal margin forming an abrupt right angle, apex of digitus a ventrally directed triangular lobe; penial valve short and broad, apex blunt, with dorsally-directed short triangular tooth, apodeme of penial valve strongly developed, at right angle to the rest of valve.
This is a montane species that occurs at mid-elevation, from 600-1500m. It is most abundant in seasonally dry to moist forest habitat and less common in cloud forest and very wet forest. It also seems more abundant in disturbed habitats than in mature forest. In Costa Rica it does well in synanthropic habitats, being common in the Central Valley and in scrubby forest on the Pacific slope in and below Monteverde.
Nests are usually in dead stems of trees, often in relatively hard wood, and usually high in the tree or otherwise highly insolated areas. Nests occasionally occur in live stems; I have collected nests from live stems of Cecropia angustifolia, Hampea appendiculata, and an unidentified lauraceous tree. It usually appears that they opportunistically use preexisting cavities rather than excavating their own. Colonies are often large and polydomous, occurring in many dead branches of multiple adjacent trees. Incipient colonies are monogynous in small dead or live stems.
Workers are diurnal foragers and may be found scattered on foliage and branch surfaces. In the field they look remarkably similar to Crematogaster and may even elevate the gaster when disturbed.
Emery, C. (1896). Studi sulle formiche della fauna neotropica. XVII-XXV. Bullettino della Societą Entomologica Italiana 28, 33–107.
Longino, J. T. (2006). A Taxonomic review of the genus Myrmelachista (Hymenoptera: Formicidae) in Costa Rica. Zootaxa 1141:1-54.
Wheeler, W. M. (1934). Neotropical ants collected by Dr. Elisabeth Skwarra and others. Bulletin of the Museum of Comparative Zoology 77, 157–240.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. firstname.lastname@example.org
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