Pseudomyrmex viduus

Nest in the living plant cavities of a wide range of plant species.

Identification
Ward (1999) - P. viduus is readily distinguished from all other species in the P. viduus group, except Pseudomyrmex vitabilis, by the elongate head (worker CI 0.70–0.79, queen CI 0.60–0.67, male CI 0.86–0.94). Other characteristic features are the closely contiguous frontal carinae (worker MFC < 0.080, queen MFC 0.054–0.090), long eyes relative to head width (worker REL2 > 0.49, queen REL2 0.56–0.61), flattened worker mesosoma, and broad profemur (both worker and queen FI 0.44–0.49). See P. vitabilis for differences from viduus.

Distribution
Mexico to Bolivia and Brazil.

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Costa Rica, Cuba, Ecuador, French Guiana, Greater Antilles, Guyana, Honduras, Mexico, Suriname, Trinidad and Tobago.

Biology
Ward (1999) - The least host-specific of the species inhabiting living plant cavities: colonies have been collected from Cordia alliodora (Ruiz & Pavon) Oken (Costa Rica), Coussapoa (Brazil), Ficus (?) branches (Colombia, Peru), Macrolobium acaciifolium (Bentham) Bentham (Ecuador), Ocotea (Costa Rica, Peru), Pseudobombax munguba (Martius & Zuccarini) Dugand (Brazil, Colombia), Pseudobombax cf. septenatum ( Jacquin) Dugand (Colombia), Pterocarpus amazonum (C. Martius ex Bentham) Amshoff (Colombia), Sapium (Brazil, Ecuador), Triplaris melaenodendron (Bertoloni) Standley & Steyermark (Costa Rica), Triplaris weigeltiana (Venezuela, Guyana), unidentified species of Triplaris (Colombia, Venezuela), and hollow stems of an unidentified Papilionoideae (Guyana). There is even a record of a colony-founding queen from Cecropia (Peru). In his study of ant-plant associations in Costa Rica, Longino (1996) noted that both Pseudomyrmex viduus and Azteca beltii Emery had exceptionally broad host ranges compared to most other plant-ants.

Earlier literature dealing with P. viduus includes Wheeler’s (1942) and Bailey’s (in Wheeler, 1942:51–52) fascinating observations on this species in Guyana (under the name P. triplaridis baileyi). They reported it to be a fierce, aggressive ant, occupying the internodes of Triplaris weigeltiana (= T. surinamensis) branches and cohabiting with the pseudococcid Farinococcus multispinosus Morrison and the coccid Cryptostigma inquilina (Newstead) (cited as Akermes secretus Morrison), in addition to nematodes and fungi that fed on the ant middens. Bailey’s examination of the food pellets of P. viduus larvae revealed not only the remains of coccoids but also those of fungal hyphae and nematodes.

In my experience the nests of this species always contain pseudococcids or coccids. In a recent collection of P. viduus from live branches of Sapium utile (7 km ESE Pto. Misahualli, Ecuador; P. S. Ward#11320) the coccids were identified as belonging to the genus Cryptostigma (plant identification by G. Webster, coccids by P. J. Gullan).

Nomenclature

 *  viduus. Pseudomyrma vidua Smith, F. 1858b: 158 (m.) BRAZIL. Combination in Pseudomyrmex: Kusnezov, 1964: 83. Senior synonym of baileyi (and its junior synonym biolleyi), caroli, sapii, tigrina (and its junior synonym trigona), ulei: Ward, 1989: 445; of opacior: Ward, 1999b: 510.
 * caroli. Pseudomyrma caroli Forel, 1899c: 89 (w.q.) COSTA RICA. Wheeler, G.C. & Wheeler, J. 1956: 382 (l.). Combination in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 382. Junior synonym of viduus: Ward, 1989: 445.
 * opacior. Pseudomyrma latinoda var. opacior Forel, 1904d: 170 (w.) CUBA. Combination in Pseudomyrmex: Kempf, 1961a: 400. Subspecies of latinoda: Wheeler, W.M. 1942: 169. Raised to species: Ward, 1990: 485. Junior synonym of viduus: Ward, 1999b: 510.
 * sapii. Pseudomyrma caroli var. sapii Forel, 1904e: 688 (w.q.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 400. Junior synonym of viduus: Ward, 1989: 445.
 * ulei. Pseudomyrma ulei Forel, 1904e: 689 (w.q.m.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 401. Junior synonym of viduus: Ward, 1989: 445.
 * baileyi. Pseudomyrma triplaridis subsp. baileyi Wheeler, W.M. 1942: 185, pl. 50 (w.q.) GUYANA. Combination in Pseudomyrmex: Kempf, 1961a: 400. Senior synonym of biolleyi: Brown, 1949a: 43. Junior synonym of viduus: Ward, 1989: 445.
 * tigrina. Pseudomyrma triplaridis subsp. tigrina Wheeler, W.M. 1942: 186 (w.m.) GUYANA. Combination in Pseudomyrmex: Kempf, 1961a: 400. Senior synonym of trigona: Brown, 1949a: 43. Junior synonym of viduus: Ward, 1989: 445.
 * biolleyi. Pseudomyrma triplaridis subsp. biolleyi Enzmann, E.V. 1944: 93 (w.) GUYANA. Junior synonym of baileyi: Brown, 1949a: 43.
 * trigona. Pseudomyrma triplaridis subsp. trigona Enzmann, E.V. 1944: 94 (w.) GUYANA. Junior synonym of tigrina: Brown, 1949a: 43.

Worker
Ward (1999) - 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.

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 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, variable in shape, subtriangular, bluntly rounded, or fin-shaped, directed ventrally or posteroventrally. In dorsal view, 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 0.010–0.020mm 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. 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 colour.

Type Material
Ward (1999):

Syntype male (unique), Ega, Amazonas, Brazil [Examined].

Pseudomyrma caroli Forel, 1899:89. Syntype workers, queens, Nicoya, Costa Rica (Alfaro) [Examined].

Pseudomyrma latinoda var. opacior Forel, 1904b:170. Holotype worker, Cuba (“coll. Ballion, ex-coll. Puls”), apparently lost, not in nor  (P. Dessart, pers. comm.).

Pseudomyrma caroli var. sapii Forel, 1904c:688. Syntype workers, queens, Bom Fim, Jurua, Amazonas, Brazil (Ule) (, MCSN, MHNG) [Examined].

Pseudomyrma ulei Forel, 1904c:689. Syntype workers, Jurua Miry, Jurua, Amazonas, Brazil (Ule) (AMNH, MCSN, MHNG, ) [Examined].

Pseudomyrma triplaridis subsp. baileyi Wheeler, 1942:185. Syntype workers, queens, Camaria, Cuyuni River, Guyana (MCZC, ) [Examined].

Pseudomyrma triplaridis subsp. tigrina Wheeler, 1942:186. Lectotype worker, Blairmont, Berbice, Guyana [Examined].

Pseudomyrma triplaridis subsp. biolleyi Enzmann, 1944:93. Syntype workers, queens, Camaria Cuyuni River, Guyana (MCZC) [Examined].

Pseudomyrma triplaridis subsp. trigona Enzmann, 1944:94. Syntype workers, males, Blairmont, Berbice, Guyana (MCZC) [Examined].