Occurs in wet forest habitats, from lowlands to cloud forest. It is most abundant in mid-elevation and cloud forest sites, decreasing in abundance at lower elevations. It inhabits leaf litter on the forest floor. (Longino, Ants of Costa Rica)
Bolton (2000) - A member of the gundlachi-complex in the Strumigenys gundlachi group. Strumigenys lalassa is closest related to Strumigenys nubila; characters linking the two are noted there. Differentiation is easy as lalassa has the postpetiole disc reticulate-punctate, lacks an apicoscrobal hair, and has no standing hairs on the mesonotum. In nubila the postpetiole disc is smooth with sparse fine longitudinal costulae, an apicoscrobal hair is present, and standing hairs occur on the mesonotum.
Longino (Ants of Costa Rica) - Mandibles in full-face view linear, elongate and narrow; ventral surface of petiole without spongiform tissue; leading edge of scape with freely projecting hairs; inner margin of mandible without a tooth or distinctly enlarged denticle at or near the midlength; labral lobes short, trigger hairs at apices of lobes long; outer margins of mandibles bowed; mandibles long (MI 67).
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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Strumigenys were once thought to be rare. The development and increased use of litter sampling methods has led to the discovery of a tremendous diversity of species. Many species are specialized predators (e.g. see Strumigenys membranifera and Strumigenys louisianae). Collembola (springtails) and other tiny soil arthropods are typically favored prey. Species with long linear mandibles employ trap-jaws to sieze their stalked prey (see Dacetine trap-jaws). Larvae feed directly on insect prey brought to them by workers. Trophallaxis is rarely practiced. Most species live in the soil, leaf litter, decaying wood or opportunistically move into inhabitable cavities on or under the soil. Colonies are small, typically less than 100 individuals but in some species many hundreds. Moist warm habitats and micro-habitats are preferred. A few better known tramp and otherwise widely ranging species tolerate drier conditions. Foraging is often in the leaf litter and humus. Workers of many species rarely venture above ground or into exposed, open areas. Individuals are typically small, slow moving and cryptic in coloration. When disturbed individuals freeze and remain motionless. Males are not known for a large majority of species.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- lalassa. Pyramica lalassa Bolton, 2000: 189, fig. 134 (w.) PANAMA. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 122
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
HOLOTYPE. TL 2.6, HL 0.66, HW 0.55, CI 83, ML 0.46, MI 70, SL 0.28, SI 51, PW 0.34, AL 0.66. Characters of gundlachi complex. Inner margin of mandible shallowly convex in proximal half, concave in distal half. Apex with 2 intercalary denticles between apicodorsal and apicoventral teeth. Preapical dentition of 5 - 8 teeth and denticles in total. Proximal of the apicodorsal tooth are two denticles, followed by two small spiniform teeth of which the distal is shorter than the proximal; sometimes a minute denticle occurs between these two teeth. Proximal of the longest spiniform preapical tooth are 1 - 4 denticles, located on the remainder of the concave section of the margin; some may be very poorly defined, low and obtuse. Eye with 5 ommatidia in the longest row. Apicoscrobal hair absent. Cephalic dorsum densely clothed with short spatulate ground-pilosity that is closely applied and directed anteriorly, but without standing hairs of any form. Pronotal humeral hair short and stout, flattened or expanded apically. Promesonotal dorsum with spatulate ground-pilosity but without any standing hairs. Disc of postpetiole reticulate-punctate. First gastral tergite and sternite smooth, the former with short basigastral costulae.
PARATYPE. TL 2.6-2.9, HL 0.66-0.74, HW 0.58-0.60, CI 81-88, ML 0.46-0.48, MI 66-72, SL 0.28-0.31, SI 48 - 52, PW 0.36-0.40, AL 0.66-0.76 (3 measured). As holotype but eye with 4 - 6 ommatidia in longest row.
The holotype and most other material entirely lacks standing hairs on the cephalic dorsum, but occasionally a widely separated pair of very short standing hairs is present close to the occipital margin.
Holotype worker, Panama: Bocas del Toro, 12-14.vii.1987, 1050 m., 8°47'N, 82°12'W, premontane rain forest (D.M. Olson) (The Natural History Museum).
Paratypes. 1 worker with same data as holotype; 2 workers, Costa Rica: Heredia Prov., La Selva, 14.iii.1987, 50 m., 10026'N, 83°59'W, #241 (D. M. Olson); 6 workers, Prov. Heredia, 17 km. S Pto Viejo, 10°l8'N, 84°02'W, 550 m., 12.ix.1985, # 1088-s, wet forest litter sample (J. Longino); 4 workers, Prov. Puntarenas, Monteverde, 1500 m., 10°l8'N, 84°48'W, 14.xii.1987, # 1980-s, cloud forest litter sample, ground (J. Longino) (University of California, Davis, BMNH, Instituto Nacional de Biodiversidad, Museum of Comparative Zoology).
- Baroni Urbani, C. & 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. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 189, fig. 134 worker described)
- Guerrero, R.J., Fernandez, F., Escarraga, M.E., Perez-Pedraza, L.F., Serna, F., Mackay, M.P., Sandoval, V., Vergara, V., Suarez, D., Garcia, E.I., Sanchez, A., Meneses, A.D., Tocora, M.C., Sosa-Calvo, J. 2018. New records of myrmicine ants (Hymenoptera: Formicidae) for Colombia. Revista Colombiana de Entomología 44: 238-259 (DOI 10.25100/socolen.v44i2.7115).