Dacetini, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Line drawing of worker face, from Brown (1959): (original, reduced).
Dark form worker, lateral view (original, reduced).
Range
Full Range: Costa Rica, Panama.
Costa Rican Range: from sea level to cloud forest elevations on Atlantic and northern Pacific slopes, apparently absent from Osa Peninsula and surrounding lowlands.
Identification
Mandibles in full-face view linear, elongate and narrow; at full closure engaging only at apex; ventral surface of petiole without spongiform tissue; leading edge of scape with freely projecting hairs; inner margin of mandible with a clearly defined submedian tooth near the midlength; labral lobes long, trigger hairs at apices of lobes short; middle preapical denticle distinctly larger than flanking denticles, similar in size to submedian tooth; mandibles relatively long (MI 61-67); mesosomal dorsum evenly convex, propodeal suture not impressed; total head length greater than 0.90mm. Also see Bolton (2000:190).
Specimens from the lowlands are light ferruginous and relatively smaller, while those from montane regions are dark brown and relatively larger (see discussion of montane dark forms). In the case of myllorhapha I have been able to detect neither morphological discontinuity between light and dark forms, nor zones of sympatry. Therefore I treat the light and dark forms as intraspecific variation in this case.
Natural History
Members of the genus are all predaceous, with a static pressure mode of attack (Bolton 1999).
Brown (1959) characterized the genus Neostruma (now part of Pyramica, see Bolton 1999) as forming
small colonies, chiefly in the leaf litter of rain forest or tropical evergreen forest, and nests occupy cavities in rotting twigs, pieces of bark or similar forest-floor vegetable debris... The food... consists primarily of small entomobryomorph Collembola and possibly some other minute terrestrial arthropods as well. Hunting behavior is like that of Smithistruma [also now part of Pyramica] rather than like the Strumigenys so far studied.
This species inhabits wet forested habitats from lowland rainforest to cloud forest. It occurs commonly in leaf litter on the forest floor but may occur in the canopy under epiphytes. Nests are known from in or under dead wood on ground.
Selected Records
Winkler samples from Hitoy Cerere, Rara Avis, Braulio Carrillo National Park to 1200m, La Selva, Penas Blancas Valley, Monteverde cloud forest, Guanacaste Conservation Area (Cerro Cacao, Pitilla).
Braulio Carrillo (Bajo La Hondura): nest in 1cm dia hollow stem of a freshly fallen canopy branch. No brood inside, only workers.
Monteverde: in Winkler sample of epiphytes and arboreal soil taken in canopy of emergent tree, 15m high.
Monteverde: nest under board in "Bull Pen" (a small pasture surrounded by cloud forest).
Penas Blancas (800m): nest in dead stick on ground.
Original Description
Neostruma myllorhapha Brown 1959:12. Holotype worker: Costa Rica [no further locality] (F. Nevermann) [MZSP].
Later moved to Pyramica. See Bolton (2000) for complete synonymy.
Taxonomic Notes
The type specimen is described as light ferruginous, mandibles and appendages more yellowish, gaster brown. Nevermann material often came from sites in the Atlantic lowlands. No doubt the type is of the lowland, light-colored form.
Literature Cited
Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). J. Nat. Hist. 33:1639-1689.
Bolton, B. 2000. The ant tribe Dacetini, with a revision of the Strumigenys species of the Malagasy Region by Brian L. Fisher, and a revision of the Austral epopostrumiform genera by Steven O. Shattuck. Memoirs of the American Entomological Institute 65:1-1028.
Brown, W. L., Jr. 1959. A revision of the Dacetine ant genus Neostruma. Breviora 107:1-13.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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