Pheidole debilis, Longino, J. T., 2009

Longino, J. T., 2009, Additions to the taxonomy of New World Pheidole (Hymenoptera: Formicidae)., Zootaxa 2181, pp. 1-90 : 23-25

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Pheidole debilis

new species

Pheidole debilis   HNS new species

Figure 4

Holotype major worker. Costa Rica, Heredia: 16km SSE La Virgen, 10.26667°N 84.08333°W, ±2000m, 1100m, 15 Feb 2001 (R. Vargas#01-RVC-015) [ INBC, unique specimen identifier INB0003622662].

Paratypes: major and minor workers. Same data as holotype; same locality as holotype but 17 Nov 2000 (J. Longino#4361) [ BMNH, CAS, FMNH, INBC, LACM, MCZ, UCD, USNM].

Geographic Range

Costa Rica.


With the morphometric profile of P. gnomus,   HNS P. mera   HNS , P. sparsisculpta   HNS , and P. sospes   HNS . Minor worker: face foveolate with overlying rugulae versus face uniformly foveolate, without overlying rugulae ( mera   HNS , sospes   HNS ) or with extensive smooth areas ( sparsisculpta   HNS ); lateral pronotum foveolate versus with smooth shiny patch ( mera   HNS ); minor worker of gnomus   HNS unknown. Major worker: vertex lobes weakly sculptured with faint foveolate sculpture versus vertex lobes with pronounced transversely arcuate rugae ( gnomus   HNS ), or coarsely reticulate rugose ( sospes   HNS ), or completely smooth and shining ( sparsisculpta   HNS ); head in lateral view normally convex versus with pronounced medial bulge on face ( gnomus   HNS ); lacking antennal scrobe versus with shallow but distinct antennal scrobe ( mera   HNS , sospes   HNS ); promesonotal groove present versus promesonotum evenly arched, with no trace of promesonotal groove ( mera   HNS ).

Description of minor worker

Measurements (paratype): HL 0.52, HW 0.49, HLA 0.17, SL 0.42, EL 0.09, ML 0.60, PSL 0.06, PMG 0.00, SPL 0.03, PTW 0.09, PPW 0.14, CI 93, SI 86, PSLI 11, PMGI 0, SPLI 6, PPI 152.

Measurements (n=13): HL 0.46-0.55, HW 0.42-0.49, SL 0.36-0.46, CI 88-93, SI 84-95.

Clypeus smooth with 1-3 longitudinal rugulae; eye small, with fewer than 10 ommatidia; face densely foveolate, overlain with reticulate rugulae; margin of vertex flattened with weak median impression; occipital carina narrow, not visible in full face view; scape with abundant subdecumbent to suberect setae, mostly shorter than maximum width of scape; promesonotal groove weakly impressed; propodeal spines present; entire mesosoma foveolate, overlain with faint reticulate rugulae on promesonotal dorsum; abundant setae on promesonotal dorsum; dorsal (outer) margin of hind tibia with short decumbent pilosity, no long erect setae; first gastral tergum smooth and shining; gastral dorsum with moderately abundant suberect setae; color variable, light to dark red brown.

Description of major worker

Measurements (holotype): HL 1.13, HW 0.94, HLA 0.30, SL 0.48, EL 0.14, ML 0.81, PSL 0.06, PMG 0.02, SPL 0.06, PTW 0.19, PPW 0.38, IHT 0.18, OHT 0.41, CI 83, SI 51, PSLI 5, PMGI 2, SPLI 6, PPI 204, HTI 43.

Measurements (n=11): HL 0.92-1.15, HW 0.80-1.04, SL 0.42-0.52, CI 81-88, SI 50-56.

Mandibles smooth and shiny; clypeus smooth and shallowly concave, with shallow anterior notch, and very weak posteromedian gibbosity or carina; face with longitudinal rugulae on cheeks and between frontal carinae, grading to faint foveolate sculpture overlain with reticulate rugulae on scrobe, fading to very faint foveolate sculpture on posterior vertex lobes; scrobe a faint, unbounded impression; head with abundant suberect setae projecting from sides of head in face view; scape smooth and shining, terete at base, with subdecumbent pubescence and scattered longer suberect setae; hypostomal margin flat; median tooth small; inner hypostomal teeth pointed, stout, closer to midline than to outer hypostomal teeth; promesonotal groove impressed; propodeal spines present; mesosoma with a mix of foveolate, smooth, and rugulose sculpture; dorsal (outer) margin of hind tibia with short decumbent pilosity, no long erect hairs; pilosity abundant on mesosomal dorsum; first gastral tergite smooth and shining, with abundant flexuous erect setae; color orange brown.


Pheidole debilis   HNS occurs in wet forest leaf litter. It is most often collected in Winkler samples of sifted litter but is rarely collected at baits. Major workers may occur together with minor workers in Winkler samples. One nest was collected in soil, and one nest was collected from rotten wood.


The name is in reference to the faint sculpture on the face of the major worker, compared to P. harrisonfordi   HNS and other common litter ants that have more heavily sculptured major workers.


This species is mainly known from the Barva Transect in Braulio Carrillo National Park, on the Atlantic slope of Costa Rica. It is moderately abundant across a range of elevations, from La Selva Biological Station to 1500m. Minor workers tentatively assigned to this species have been collected elsewhere in Costa Rica: Hitoy Cerere, the Monteverde area, and the southern Pacific lowlands. A collection of minor workers in a Winkler sample from the Osa Peninsula also contained a major worker that matches the typical form in most respects, differing in the lack of any clypeal gibbosity or carina, and the presence of shiny patches on the antennal scrobes.

In Costa Rica, minor workers of this species can be distinguished from the common P. harrisonfordi   HNS by more pronounced rugulae on the face and mesosomal dorsum, the slightly impressed promesonotal groove, and the lack of any longer setae above the short, subdecumbent pilosity on the hind tibia. However, these distinctions do not hold over the broad concept of P. harrisonfordi   HNS as a whole (see Comments under P. harrisonfordi   HNS ). Minor workers are distinguished from the similar P. beloceps   HNS by the foveolate side of the pronotum (smooth and shiny on P. beloceps   HNS ). Major workers are distinguished from P. beloceps   HNS by having a relatively broader head and having the scrobe foveolate (small shiny patches on P. beloceps   HNS ).

Additional material examined

COSTA RICA: Heredia, La Selva Biological Station, 10°25'N, 84°01'W, 50m (numerous collectors and collections); 16km SSW Pto. Viejo, 10°19'03"N, 84°02'56"W, 500m (numerous collectors and collections); Cantarrana, 11km ESE La Virgen, 10°20'43"N, 84°03'28"W, 300m (numerous collectors and collections); Vara Blanca, 10km NE Vara Blanca, 10°14'N, 84°05'W, 1500m (numerous collectors and collections); Limon, Hitoy Cerere Biol. Reserve, 9°40'N, 83°02'W, 200m (J. Longino); Puntarenas, Monteverde, 10°18'N, 84°48'W, 1500m (L. A. Schonberg); Bijagual, Carara Biol. Reserve, 9°47'N, 84°36'W, 500m (J. Longino); Est. Biol. Los Llanos, near Santa Elena, 10°18'18"N, 84°50'14"W, 1150m (J. Longino); 13km SSW Pto. Jimenez, 8°24'24"N, 83°19'42"W, 130m (J. Longino).


Costa Rica, Santo Domingo de Heredia, Instituto Nacional de Biodiversidad (INBio)


United Kingdom, London, The Natural History Museum [formerly British Museum (Natural History)]


USA, California, San Francisco, California Academy of Sciences


USA, Illinois, Chicago, Field Museum of Natural History (also used by Finnish Museum of Natural History)


USA, California, Los Angeles, Los Angeles County Museum of Natural History


USA, Massachusetts, Cambridge, Harvard University, Museum of Comparative Zoology


USA, California, Davis, University of California, R.M. Bohart Museum of Entomology


USA, Washington D.C., National Museum of Natural History, [formerly, United States National Museum]













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