Pseudomyrmex opaciceps Ward

Ward, Philip S., 1993, Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae), Journal of Hymenoptera Research 2, pp. 117-168: 159-160

publication ID 10.5281/zenodo.10150

publication LSID


persistent identifier

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scientific name

Pseudomyrmex opaciceps Ward

sp. nov.

Pseudomyrmex opaciceps Ward  , sp. nov.

(Fig. 5)

Holotype worker. - GUATEMALA Retalhuleu: Puente Samala, 3.8 mi. NE San Felipe , 24.vii. 1966, D. H. Janzen W006724966 ( LACM). HW 1.43, HL 1.42, EL 0.85, PL 0.89, PH 0.39  .

Paratypes, - Series of 11 workers with same data as holotype;  large series of ca. 60 workers and 10 males with the same locality and collector as holotype but the following dates and collection numbers: 18.vii.1966 M002718966 (possibly mis-labelled - see below), 18.vii.1966 W002718966, 18.vii.1966 W004718966, 18.vii.1966 W005718966 (possibly mis-labelled - see below), 23.vii.1966 W002723966, 24.vii.1966 W001724966, 24.vii.1966 W 003724966 (  BMNH,  LACM,  MCZC,  MZSP,  PSWC,  UCDC,  USNM)  .

Additional non-type material. - Series of workers, queens, and males from six additional localities. MEXICO Chiapas: 94.5 mi. SE Tonola (D. H. Janzen)  . GUATEMALA Retalhuleu: 2 mi. N Puente Samala, 3.8 mi. NE San Felipe (D. H. Janzen)  ; 3 mi. N Puente Samala, 3.8 mi. NE San Felipe (D. H. Janzen)  ; 5 mi. W Retalhuleu, Hwy. CA-2 at Rio Nil (D. H. Janzen)  ; Guatemala: Ciudad de Guatemala (D. H. Janzen)  . EL SALVADOR La Libertad: Quezaltepeque (M. Irwin & D. Cavagnaro) ( LACM,  MCZC,  PSWC)  .

Worker measurements (n=14). - HL 1.30-1.42, HW 1.33-1.43, MFC 0.040-0.058, Cl 0.99-1.04, REL 0.57-0.61, REL2 0.56-0.61, OOI 0.14-0.68, VI 0.65-0.71, FCI 0.029-0.042, SI 0.46-0.50, SI2 0.77-0.88, FI 0.36-0.39, PDI 1.12-1.37, MPI 0.059- 0.076, NI 0.65-0.70, PLI 0.42-0.47, PWI 0.38-0.43, PPWI 0.92-1.16.

Worker diagnosis. - With the traits of the P. gracilis  group (see couplet 6 of key) and the following more specific features. Head about as broad as long; anterior margin of median clypeal lobe straight to weakly convex; pronotum with blunt dorsolateral margination; mesonotum more steeply inclined than basal face of propodeum; petiole long and slender (see PLI and PWI values) with a distinct anterior peduncle (Fig. 6); head densely punctulate-coriarious and matte; standing pilosity abundant, pale silvery-white, not black. Color: head and mesosoma dark brown to black, mandibles and appendages lighter brown; petiole, postpetiole and gaster a contrasting pale luteous brown or orange-brown. Portions of the fronto-clypeal complex, malar area, and mandibles may also be luteous brown.

Taxonomic comments. - This species is distinguished from the closely related and sympatric P. gracilis  by a modest but consistent difference in head sculpture. In workers and queens of P. opaciceps  the punctulate-coriarious sculpture and associated dense pubescence obscure the sheen of the head, producing a matte appearance under soft light, while in P. gracilis  the head remains at least weakly shining. In addition the workers and queens of P. opaciceps  average smaller in size than those of P. gracilis  and they have a more slender petiole ( PLI <0.48; see Figs. 5,6,53). Finally, P. opaciceps  has a distinctive and largely invariant color pattern: the pale yellow or orange-brown petiole, postpetiole and gaster contrast with the much darker head and mesosoma. This is not observed in Central American P. gracilis  , although a similar color pattern occurs in some Colombian populations of P. gracilis  , and it also seen in some individuals of the more distantly related South American species P. venustus (F. Smith)  .

Among the P. opaciceps  paratypes in LACM, the pinned specimens with Janzen collection numbers M002718966 and W005718966 appear to have been mis-labelled. In the Janzen alcohol collection samples M002718966 and W005718966 contain colony series of two quite different species (in the P. ferrugineus  and P. pallidus  groups, respectively); but there are two other alcohol samples from the same date and locality ( W 002718966 and W 004718966) which are of P. opaciceps  . I conclude that a frame-shift occurred in the process of labelling the pinned series of specimens, producing the labelling error (this has happened to a substantial number of P. ferrugineus  group collections - see "Materials and Methods" section). The remaining paratype (and non-type) material of P. opaciceps  appears to be correctly labelled.

Biology. - P. opaciceps  is evidently a generalist twig-nesting Pseudomyrmex  , but Janzen also collected it from an Acacia cornigera  View Cited Treatment tree overgrown by vines and unoccupied by the P. ferrugineus  group (5 mi. W Retalhuleu, Guatemala, collection numbers M 010714966- A and M 010716966- D).


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


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


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