Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Identification
Minor worker: head length 0.67mm, head width 0.63mm, scape length 0.75mm, Webers length 0.83mm (n=1). Head flattened, subcordate behind; mesonotal and metanotal grooves well-impressed; propodeal spines of moderate length; face and mesosoma uniformly foveolate; gastral dorsum foveolate anteriorly, fading to smooth at posterior border; dorsal pilosity abundant, short, somewhat stiffened; color orange.
Major worker: head length 1.33mm, head width 1.33mm, scape length 0.80mm (n=1). Face uniformly foveolate, overlain with weak rugae between eyes and antennal insertions; hypostomal margin with pair of teeth, teeth spiniform, widely separated, partially overlapping recessed teeth flanking mandibles; dorsal pilosity sparse; head with sparse, appressed, silky pubescence, and no setae projecting from sides of head in face view.
Taxonomically, radoszkowskii is a polytypic species with the nominal plus ten subspecies. The species complex occurs throughout the Neotropics. One subspecies, pugnax, has its type locality in Costa Rica (Alajuela). We see evidence for two species in the radoszkowskii complex in Costa Rica, pugnax and luteola. pugnax is geographically variable within Costa Rica. A syntype of pugnax at the MCZ most closely matches material we have examined from the Monteverde area. We retain the trinomial nomenclature only to conform to the current taxonomic status of the name, not to imply any biological significance of subspecies vs. species rank.
Range (pugnax)
Honduras, Costa Rica (Pacific lowlands and slopes to 1500m).
Natural History
This is one of the most common ants in the Pacific lowlands of Costa Rica. It is abundant in open areas, disturbed habitats, and second growth vegetation. Nests are in the soil, and workers forage over the surface and into low vegetation.
Selected Records
Guanacaste Conservation Area (Pitilla): workers on road.
Guanacaste Conservation Area (Maritza): common at baits.
Curu Biological Reserve: workers emerging in large numbers from cracks and holes in the soil.
Santa Rosa National Park: Seasonal dry forest; at baits; nest about 10cm deep in soil.
Monteverde and San Luis: occurs commonly in pastures; common at baits; nest entrance observed in bare soil, from which workers were recruiting 10cm to hamburger.
Carara Biological Reserve: mature wet forest; nest under bark flap of common understory tree, 1.5m high.
Manuel Antonio National Park: wet forest; at baits and in Winkler samples.
Corcovado National Park: common at extrafloral nectaries on low vegetation; several nests observed in soil; workers once observed attacking a live millipede much larger than they.
Corcovado National Park: a dilleniaceous vine (dense, long, erect pubescence) had many minors on the new growth (for unknown reason, no obvious nectaries, no Homopterans). A column led down the stem to a tree base. A thin layer of leaf litter covered an entrance hole in red clay soil. I spent several minutes pestering ants at the entrance, and I dropped a Rogeria at the entrance, but no majors appeared. I dug down, and at about 10cm depth I began hitting majors and brood. The majors began running about, but were very timid.
Corcovado National Park: ants were tending membracids on newgrowth tips of Machaerium. Freshly killed tabanids impaled on thorns behind the shoot tips were ignored for an hour before recruitment ocurred, even though there was a steady flow of workers passing them. In contrast, tabanids placed near a lone forager 20m further along the trail were recruited to immediately.
Page authors:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA. scover@oeb.harvard.edu
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