Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Costa Rica (Atlantic lowlands). A. emarginatus complex: Belize and Honduras south to Amazonian Brazil, caribbean islands.
Identification
Combined length of head and closed mandibles greater than 2.2mm; medial borders of mandibles with two or more prominent, serially arranged teeth (in addition to the 3 teeth at apex).
Natural History
Anochetus are presumably predators, using their snapping mandibles much like their larger relatives, Odontomachus. However, there are few direct observations. A. striatulus nests in the low arboreal zone in wet forest, under epiphytes and in carton nests.
These images show a typical nest (lateral view, 70k, 350k; orange in photos is piece of old trail flagging on sapling; dorsal view, 70k, 350k). The images were taken near the El Ceibo station in Braulio Carrillo National Park in June 2002. The nest was about 1m high on the trunk of a small tree sapling. There was a cluster of epiphyte roots comprised of aroid stems climbing the trunk, and the roots of a large Codonanthe(?) and some other small seedlings. The matrix was composed of vegetation fragments, especially visible on top as a loose pile of small fragments that appeared to be dried stipules or bracts of some kind. The workers came boiling out on disturbance.
Chris Starr and students (pers. comm.) have studied the closely related A. emarginatus in Trinidad, and conclude that it does not have normal winged queens. Instead colonies have gamergates (reproductive workers). I have never collected alate queens of striatulus, and so it is possible that striatulus has a similar reproductive biology.
Selected records
Heredia: Casa Plastico, 17km S Pto. Viejo, 10¡18'N, 84¡2'W, 550m (J. Longino). Wet forest; carton nest on treetrunk.
Heredia: 22km N Volcan Barba, 10¡20'N, 84¡4'W, 500m (J. Longino). Primary wet forest; colony in 2m high root mat on tree trunk.
Limon: Hitoy Cerere Biological Reserve, 9¡40'N, 83¡2'W, 100m (J. Longino). Primary forest at river edge; nest in rotten knot covered with debris.
San Jose: Carrillo, Braulio Carrillo National Park, 10¡09'N, 83¡55'W, 500m (J. Longino).
Taxonomic Notes
The emarginatus complex is widespread in the Neotropics (Brown 1978). Brown left the complex largely unresolved because of the paucity of material. He described variation in the male genitalia that suggested multiple species occur within the complex, but sharp distinctions were not possible among the workers.
Two described taxa, striatulus and micans, are relevant to Costa Rican material of this complex. A. striatulus was described by Emery (1890), with types from Jimenez, near modern day Guapiles. A. micans was described by Forel (1908) as a variety of subspecies testaceus [a quadrinomial and thus unavailable; first made available by Brown (1978), as a binomial], with types from "Altos del Cangrejal de Aserri, cote Pacifique de Costa-Rica, 1000 metres." The brief description of micans reads "It is interesting to find on the mainland this subspecies from the Antilles. The specimens are more sculptured than the type [of emarginatus or testaceus?], the head and pronotum almost entirely mat, color not as dark." Brown treated A. striatulus as an allopatric or parapatric variant within the emarginatus complex, and reported a second collection (by Brown) from near the Rio Toro Amarillo, near Guapiles. He maintained micans as a distinct species, and identified as micans scattered material from Belize, Honduras, and the Bahamas (he placed them under micans as a matter of convenience rather than because of strong evidence of conspecificity). In his key he distinguished striatulus and micans as follows:
striatulus: body dark reddish-brown, including head (corners of head slightly paler), legs brownish-yellow; frontal area, front and sides of pronotal disc, and upper front face of petiolar node finely striolate, sericeous; posterior center of pronotal disc smooth and shining; petiolar teeth long (L 0.1mm or more) and sharp.
micans: body light ferruginous; pronotum striate at least over front half; sculpture and petiolar teeth varying with locality.
I have now examined four different collections of what I call striatulus from four different Atlantic slope localities. They vary considerably in the extent of sculpture on the pronotum, and all are similarly red-brown. At this point there is no evidence for sympatric members of this complex in Costa Rica, nor clearly differentiated allopatric or parapatric forms. I use the name striatulus for Costa Rican material, with micans a likely synonym.
At this point there is also no strong distinction between the material discussed here and emarginatus sensu stricto. A. emarginatus was described by Fabricius in 1804, from a type specimen from "America meridionali." Future research may result in striatulus and micans being synonyms of emarginatus.
Type data
Anochetus (Stenomyrmex) emarginatus r. striatula Emery 1890:64. Syntype worker: Costa Rica: Jimenez.
Literature Cited
Brown, W. L., Jr. 1978. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section B. Genus Anochetus and bibliography. Studia Entomol. 20:549-652.
Emery, C. 1890. Voyage de M. E. Simon au Venezuela. Formicidae. Annls Soc. Entomol. Fr. 19:55-76.
Fabricius, J. C. 1804. Systema Piezatorum. Brunsvigae: C. Reichard. xiv + 15-439 + 30pp. Ants - p. 395-428.
Forel, A. 1908. Fourmis de Costa-Rica recoltees par M. Paul Biolley. Bull. Soc. Vaud. Sci. Nat. 44:35-72.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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