Pseudomyrmex particeps Ward

Ward, Philip S., 1993, Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae), Journal of Hymenoptera Research 2, pp. 117-168: 146

publication ID 10.5281/zenodo.10150

publication LSID


persistent identifier

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scientific name

Pseudomyrmex particeps Ward

sp. nov.

Pseudomyrmex particeps Ward  , sp. nov.

(Figs. 14, 23, 54, 57, 72)

Holotype worker. - COSTA RICA, Puntarenas: Rincon, Peninsula Osa , 3.iii. 1965, D.H. Janzen #111 ( LACM). HW 0.83, HL 1.10, EL 0.50, PL 0.50, PH 0.31  .

Paratypes. - Same data as holotype: series of 82 workers, 14 males, one queen (  AMNH,  BMNH,  CASC,  GBFM,  INBC,  JTLC,  LACM,  MCZC,  MZSP,  PSWC,  UCDC,  USNM). Additional non-type material listed below  .

Worker measurements (n = 12). - HL 0.93-1.10, HW 0.77-0.83, MFC 0.037-0.050, Cl 0.75-0.84, REL 0.44-0.48, REL2 0.55-0.60, OOI 1.47-1.96, VI 0.65-0.75, FCI 0.048-0.062, SI 0.45-0.49, SI2 0.78-0.83, NI 0.53-0.62, PLI 0.58-0.66, PWI 0.55- 0.60, PPWI 1.03-1.26.

Worker diagnosis. - Very similar to P. nigrocinctus  (q.v.) except as follows. Eyes longer ( REL 2 0.55-0.60, EL / LHT 0.59-0.64) (Figs. 14, 42, 43). Front of head more strongly shining. Medium to dark brown; gaster uniformly dark brown or black; mandibles, fronto-clypeal complex, and appendages lighter brown.

Comments. - P. particeps  is obviously a very close relative of the allopatric P. nigrocinctus  , but there are consistent differences between the two in eye size and color which exceed the limits of variation seen throughout the much wider range of P. nigrocinctus  . Workers in the type series of P. particeps  also have more elongate heads than those of P. nigrocinctus  but this distinction is not seen in other samples. Differences between queens of the two species are more striking with the two known queens of P. particeps  having more elongate heads (Cl≈0.61, compared with 0.67-0.72 in a sample of 13 P. nigrocinctus  queens) and longer metatibiae relative to head width ( LHT / HW ≈1.12 versus 0.97-1.07 in P. nigrocinctus  ). Additional alates of P. particeps  are needed to confirm these differences and the apparent distinctions in male genitalia (see male key).

Distribution and biology. - P. particeps  is a rare species known only from the Osa Peninsula and one adjacent locality, in Costa Rica (Fig. 72). It appears to be associated exclusively with Acacia allenii View Cited Treatment   , a forest species (see Janzen, 1974 for more information aboutthehostplant). In contrast, P. nigrocinctus  is found farther north in more open habitats where it typically inhabits Acacia collinsii View Cited Treatment   . The differences in worker morphology between P. particeps  and P. nigrocinctus  (darker color and more elongate head and/or eyes in the former) parallel those observed between populations of P. spinicola  from the same areas (see below under P. spinicola  ), suggesting similar selection pressures associated with more forested habitats and partial ( P. spinicola  ) or exclusive ( P. particeps  ) occupancy of a different Acacia  species.

Material examined. Type material listed above, plus the following ( JTLC,  LACM,  PSWC). -  COSTA RICA Puntarenas: 4mi S Rincon (D.H.Janzen)  ; Bahia Drake, Osa Penin . (FJoyce)  ; Corcovado Natl. Pk., Sirena , 50m (J.T.Longino)  ; Rincon (A.R.Moldenke)  ; San Jose: 16.7mi SW San Isidro on Hwy. 22, 160m (D.H.Janzen)  .


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


USA, New York, New York, American Museum of Natural History


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


USA, California, San Francisco, California Academy of Sciences


Panama, Panama, Universidad de Panama


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


John T. Longino


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


Brazil, Sao Paulo, Sao Paulo, Museu de Zoologia da Universidade de Sao Paulo




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]