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Pseudomyrmex viduus (F. Smith, 1858)


Worker diagnosis. A member of the Pseudomyrmex viduus group, with an elongate head (CI 0.70-0.79), closely contiguous frontal carinae (worker MFC < 0.080), long eyes relative to head width (REL2 0.50-0.57), flattened mesosoma, broad profemur (FI 0.44-0.49), and relatively small size (HW < 1.00). Median clypeal lobe rounded anterolaterally. Petiole shape as illustrated, anteroventral process well developed. Head sculpture consisting of dense punctures on anterior half of head (separated by about their diameters or less), becoming sparser and more unevenly spaced posteriorly. Standing pilosity and appressed pubescence common on most of body. Standing hairs present on posterior margin of head, on mesosoma (MSC 45-88) and on tibiae (HTC 8-18). Body concolorous medium- to dark-brown, the appendages lighter; gaster sometimes darker than the rest of the body.
See a detailed description of worker below.

Comments. P. viduus can be distinguished from all other members of the P. viduus group, except P. vitabilis, by its elongate head (worker CI 0.70-0.79, queen CI 0.60-0.67, male CI 0.86-0.94) and elongate eyes (worker REL2 0.50-0.57, queen REL2 0.56-0.61). P. vitabilis, which is known only from a single queen from the Colombian Amazon, can be separated from P. viduus by its more extreme elongation and smaller size (queen CI 0.56, queen HW 0.71).

Map of Pseudomyrmex viduus DistributionDistribution and biology. P. viduus is a wide-ranging species, distributed from Mexico to Bolivia and Brazil, with an unconfirmed record from Cuba. In contrast to most Pseudomyrmex species, the workers are very aggressive and sting readily. Colonies inhabit live plant cavities (domatia), in which they keep brood and scale insects (Pseudococcidae and Coccidae). P. viduus has been recorded from a diverse assemblage of ant-plants, including Cordia alliodora (Costa Rica), Coussapoa (Brazil), Macrolobium acaciifolium (Ecuador), Ocotea (Costa Rica, Peru), Pseudobombax (Brazil, Colombia), Pterocarpus amazonum (Colombia), Sapium (Brazil, Ecuador), and Triplaris (Costa Rica, Colombia, Venezuela, Guyana). Further details on biology can be found in Wheeler (1942), Longino (1996), and Ward (1999b).

Pseudomyrmex viduus: full synonymy

Pseudomyrma vidua F. Smith, 1858A:158. Syntype male (unique), Ega , Amazonas, Brazil (BMNH)

Pseudomyrma caroli Forel, 1899F:89. Syntype workers, queens, Nicoya, Costa Rica (Alfaro) (MCSN, MHNG) [Synonymy by Ward, 1989:445].

Pseudomyrma latinoda var. opacior Forel, 1904E:170. Holotype worker, Cuba (“coll. Ballion, ex-coll. Puls”), apparently lost, not in ISNB nor LMSG (P. Dessart, pers. comm.). [Synonymy by Ward, 1999B].

Pseudomyrma caroli var. sapii Forel, 1904F:688. Syntype workers, queens, Bom Fim, Jurua, Amazonas, Brazil (Ule) (AMNH, MCSN, MHNG) [Synonymy by Ward, 1989:445].

Pseudomyrma ulei Forel, 1904F:689. Syntype workers, Jurua Miry, Jurua, Amazonas, Brazil (Ule) (AMNH, MCSN, MHNG, NHMB) [Synonymy by Ward, 1989:445].

Pseudomyrma triplaridis subsp. baileyi Wheeler, 1942:185. Syntype workers, queens, Camaria, Cuyuni River, Guyana (MCZC, USNM) [Synonymy by Ward, 1989:445].

Pseudomyrma triplaridis subsp. tigrina Wheeler, 1942:186. Lectotype worker, Blairmont, Berbice, Guyana (MCZC) [Synonymy and lectotype designation by Ward, 1989:445].

Pseudomyrma triplaridis subsp. biolleyi Enzmann, 1944:93. Syntype workers, queens, Camaria, Cuyuni River, Guyana (MCZC) [Synonymy, under P. triplaridis baileyi, by Brown, 1949A:43].

Pseudomyrma triplaridis subsp. trigona Enzmann, 1944:94. Syntype workers, males, Blairmont, Berbice, Guyana (MCZC) [Synonymy, under P. triplaridis tigrinus, by Brown, 1949A:43].

Pseudomyrmex caroli (Forel); Wheeler & Wheeler, 1956:382 [Description of larva].

Pseudomyrmex viduus (F. Smith); Kusnezov, 1964:83 [First explicit combination in Pseudomyrmex].

Pseudomyrmex viduus (F. Smith); Ward, 1989:445 [Brief characterization].

Pseudomyrmex viduus: detailed description of worker

Worker measurements (n= 35). HL 0.94-1.30, HW 0.74-0.97, MFC 0.047-0.079, LHT 0.63-0.88, CI 0.70-0.79, REL 0.39-0.44, REL2 0.50-0.57, FCI 0.05-0.09, SI 0.44-0.50, FLI 1.27-1.67, FI 0.44-0.49, PLI 0.75-0.92, PWI 0.73-0.92, PPWI 1.31-1.70.

Worker description. Relatively small species (HW < 1.00). Masticatory margin of mandible with 6 (rarely 5 or 7) teeth. Palp formula 5,3. Median clypeal lobe anterolaterally rounded (not sharply angulate), its anteromedial surface deflected ventrally. Frontal carinae less well separated than in most species of the P. viduus group (MFC < 0.080, PFC < 0.120), tending be parallel or slightly converging along most of their course and then more strongly converging posteriorly (ASM >= PFC > MFC). Median lobes of antennal sclerites relatively well exposed (PFC/ASD 0.52-0.64; FCI2 0.31-0.53). Scape expanded distally to twice its basal width; funiculus short, also expanded apically, the terminal segment about 1.4-1.6 times the width of the first segment; funicular segment 2 about as broad as, or broader than, long; funicular segments 3-10 notably broader than long. Head elongate (CI < 0.80), the sides relatively straight, usually diverging slightly posteriorly; side of head rounding relatively gradually into the posterior margin, which is concave in frontal view. Mesosoma dorsum more or less flattened, metanotal groove moderately incised (MP 0.034-0.077); dorsal face of propodeum somewhat longer than the declivitous face (PDI 1.01-1.51), and meeting the latter at a well rounded angle. Metapleural gland bulla well-developed and conspicuous. Profemur broad (FI > 0.43) and legs relatively short, LHT/HL 0.63-0.71. Petiole as in Fig. 15, slightly longer than high (PLI < 0.93), with a weakly differentiated anterior peduncle, followed by an increasingly convex anterodorsal face which rounds into the posterior face; posterior face appearing only slightly steeper than anterior face (lateral view). Summit of node behind the midpoint of the petiole (NI 0.51-0.63). Anteroventral petiolar process usually well developed (Fig. 15), variable in shape, subtriangular, bluntly rounded, or fin-shaped, directed ventrally or posteroventrally. In dorsal view (Fig. 26), the minimum (anterior) width of petiole about half the maximum width (PWI3 0.44-0.56). Postpetiole notably broader than long (PPWI > 1.30); ventral protrusion of postpetiolar sternite prominent and anteroventral process of postpetiole moderately well developed. Mandible generally sublucid, with scattered elongate punctures and overlying fine striolation. Sculpture on dorsum of head somewhat variable, punctures on the anterior half to two thirds of head relatively dense, evenly spaced, mostly 0.010-0.020 mm in diameter, and separated by about their diameters or less; punctures on upper third of head less dense and more unevenly spaced, separated by several to many diameters, the interspaces either smooth and shiny or very weakly coriarious. Mesosoma dorsum sublucid, with numerous piligerous punctures (separated by one to several diameters); side of mesosoma with sculpture less uniform, with a tendency towards the development of more extensive smooth shiny or weakly coriarious interspaces on parts of the mesopleuron which contrasts with coarser imbricate-punctulate and imbricate-costulate sculpture adjacent to this on the posterior margin of the mesopleuron, on the metapleuron and on the lateral propodeum. Petiole, postpetiole and gaster sublucid, the reflectance dulled (especially on the gaster) by fine punctulae and associated appressed pubescence. Standing pilosity common (MSC 45-88, HTC 8-18); standing and decumbent hairs conspicuous on the posterior margin of head (frontal view) but absent or sparse along the sides (Fig. 4). Appressed pubescence well developed, most conspicuous on the mesosoma, petiole (sparse medially in some individuals), postpetiole and gaster; postpetiole and abdominal tergite IV with appressed hairs separated by much less than their lengths. Body generally concolorous medium- to dark-brown, although in some populations the gaster is darker than rest of body; antennae, frontoclypeal complex, side of head, and distal portions of legs tending to be lighter yellow- or orange-brown in color.

Literature Cited

  • Longino, J. T. 1996. Taxonomic characterization of some live-stem inhabiting Azteca (Hymenoptera: Formicidae) in Costa Rica, with special reference to the ants of Cordia (Boraginaceae) and Triplaris (Polygonaceae). Journal of Hymenoptera Research 5:131-156.
  • Ward, P. S. 1999b. Systematics, biogeography and host plant associations of the Pseudomyrmex viduus group (Hymenoptera: Formicidae), Triplaris– and Tachigali-inhabiting ants. Zoological Journal of the Linnean Society 126:451-540.
  • Wheeler, W. M. 1942. Studies of Neotropical ant-plants and their ants. Bulletin of the Museum of Comparative Zoology 90:1-262.

For the taxonomic references cited under “full synonymy” see the complete list of taxonomic literature on Pseudomyrmecinae

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