Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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SEM images of worker: whole worker lateral view (reduced, original); head, face view (reduced, original); head, lateral view (reduced, original); antenna (reduced, original); clypeus (reduced, original).
Range
Costa Rica is the type locality. I have seen horni-like material from Colombia, Mexico (Chiapas and Veracruz), and Panama, but given the taxonomic uncertainty of species boundaries in the testacea group (see Genus Overview), I am reluctant to make any statements about the range outside of Costa Rica. In Costa Rica this species occurs in wet to moist forests throughout the country, from near sea level to cloud forests at 1700m. It is more abundant in montane and cloud forest than in lowland rainforest.
Identification
Antennae 8-9 segmented; interantennal lamella subrectangular in lateral view; in face view anterior margin of clypeus shallowly convex to flat; interantennal lamella lacking an anterior tooth in side view; color red brown to nearly black (antennal club contrastingly yellow on dark specimens).
Similar species: testacea. The definition of this species is uncertain; see the figures and discussion of geographic variation under Genus Overview.
Natural History
Discothyrea are extremely small, cryptobiotic inhabitatants of forest leaf litter (see Genus Overview). In Costa Rica, workers and queens of horni are relatively common in berlese samples of soil/litter, and in Winkler samples of sifted leaf litter.
Annotated list of material examined
La Selva: numerous workers and queens from 8 berlese samples, 3 Winkler samples, and a student survey of leaf litter fauna.
Braulio Carrillo National Park, elevational transect above La Selva: two workers from 300m, and a queen from 550m match La Selva horni.
Hitoy Cerere Biological Reserve: one worker from Winkler sample; similar to La Selva material but clypeus not as truncate.
Penas Blancas Valley: 8 workers, 1 queen, from 4 different Winkler samples; similar to La Selva material.
Monteverde: workers and queens from 15 different Winkler samples; similar to La Selva material, but darker brown color and larger size on average. These are most similar to the type.
Osa Peninsula, Manuel Antonio, Carara: 5 workers from 4 Winkler samples; similar to La Selva horni, but color light orange brown, size averaging smaller.
Type data
Discothyrea horni Menozzi 1927:270. Holotype queen: Costa Rica, San Jose (Schmidt) [DEIC] (examined).
Discothyrea isthmica Weber 1940:78. Holotype queen: Panama, Barro Colorado Island (Williams) [MCZC] (examined). PROPOSED NEW SYNONYMY. Measurements: HW 0.427, HL 0.471.
I examined the type of horni in 1990. It matched the montane dark form typical of Monteverde cloud forest. Much of Schmidt's material was collected in montane forests around San Jose, such as Vara Blanca. I examined the type of isthmica in 1999. It matched horni specimens from the Costa Rican lowlands.
Literature Cited
Menozzi, C. 1927. Formiche raccolte dal Sig. H. Schmidt nei dintorni di San Jose di Costa Rica. Entomol. Mitt. 16:266-277.
Weber, N. A. 1940. Rare Ponerine genera in Panama and British Guiana (Hym.: Formicidae). Psyche 47:75-84.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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