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PSEUDOMYRMEX FERRUGINEUS GROUP
Worker, diagnosis. - Medium sized species ( HW 0.74-1.26, HL 0.86-1.42); head varying from moderately elongate to rather broad (Cl 0.75-0.97), with relatively short eyes ( REL 0.39-0.50, REL 2 0.45- 0.62) (Figs. 10-19). Masticatory margin of mandible with 6, rarely 7, teeth, MD8/MD9≈0.70; mesial tooth on basal margin notably closer to apicobasal angle than to proximal tooth, MD4/ MD5≈0.74. Palp formula 5,3, reduced to 4,3 in two species. Anterior margin of median clypeal lobe somewhat blunt-edged, in dorsal view convex, straight or concave, laterally rounded or with sharp angles. Frontal carinae separated by about basal scape width in most species but more closely contiguous in two ( FCI 0.03-0.10, FCI 2 0.24-0.75, ASI 0.52-0.73), fusing anterolaterally with antennal sclerites. Funicular segments II and III about as broad as long ( FLI 1.46-2.45). Profemur slender ( FI 0.35-0.41). Pronotum laterally rounded. Metanotal groove well marked ( MPI 0.04-0.09). Basal and declivitous faces of propodeum moderately well differentiated and subequal in length ( PDI 0.94- 1.30), in profile the juncture between the two subangulate or gently rounded (Figs. 20-29). Petiole relatively long ( PL / HL 0.44-0.63), always much longer than high or wide ( PLI 0.47-0.71, PWI 0.46- 0.75), small anteroventral tooth present; in two species anterior peduncle of petiole weakly differentiated and posterolateral comers of petiolar node not expanded (these are presumably the plesiomorphic conditions in the group), in other species petiole with distinct anterior peduncle and with expanded, (sub)angulate posterolateral corners. Postpetiole broader than long ( PPWI 1.03- 1.85), with small anteroventral tooth. Body sculpture varying from densely punctulate or punctulate-coriarious to coriarious-imbricate, the integument sublucid to opaque; dorsum of head never with extensive smooth, shiny interspaces (punctulae usually separated by their diameters or less); propodeum of some species overlain by a coarser but weak rugulo-punctate sculpture. Standing pilosity common, present on the scapes, head, entire mesosoma dorsum (10 or more standing hairs visible in profile), petiole, postpetiole and gaster,
absent from the extensor faces of tibiae. Appressed pubescence dense on most of body, including head and abdominal tergite IV. Color varying from light yellow- or orange-brown to black.
Queen diagnosis. - Similar to worker except for caste-specific differences. Larger in size ( HW 0.76- 1.36, HL 1.05-1.81), head more elongate (Cl 0.60- 0.80). Ocular indices differing slightly: REL 0.38- 0.48, REL2 0.51-0.70. Median clypeal lobe narrower and more protruding, anterior margin convex or straight, laterally rounded or subangulate. Petiole and postpetiole generally more slender ( PL / HL 0.57-0.72, PLI 0.43-0.63, PWI 0.47-0.67, PPWI 1.06-1.50). Forewing with 2 cubital cells.
Male, diagnosis. - Head varying from longer than broad to slightly broader than long (Cl 0.82- 1.04 in a sample of 70 males belonging to all species); compound eye large, prominent ( REL 2 0.49-0.62). Mandibles with 8+ teeth or denticles on masticatory margin. Palp formula as in females, but somewhat more variable (males with 5p4,3 commoner than in workers or queens). Surface of median clypeal lobe convex, its anterior margin subtriangular in shape (dorsal view) with sides converging medially to a rounded point. Petiole and postpetiole more slender than in workers ( PLI 0.40-0.55, PWI 0.35-0.51) and simpler in shape. Posterolateral comers of sternites IV-VIII not notably protruding ventrally. Subgenital plate (sternite IX) with a conspicuous posteromedial concavity (Figs. 54, 55). Posterior margin of pygidium (tergite VIII) convex, directed posteroventrally. Paramere with several characteristic features: a finger-like, posterodorsally directed mediodorsal lobe; angulate or expanded posterodorsal extremity; and mesial dorsoventral ridge which joins the mediodorsal lobe posteriorly. Aedeagus with expanded posterodorsal comer, a medial protrusion on the posterior margin,numerous small teeth (15+) on the posterior margin, and on the outer face a raised ridge curving posterodorsally from a basal origin.
Comments. - Workers and queens of the P. ferrugineus group can be distinguished from all other Pseudomyrmex by their possession of the following combination of traits: mandibles with 6- 7 teeth; palp formula 5,3 or 4,3; standing pilosity common on mesosoma dorsum but absent from external faces of tibiae; worker metanotal groove conspicuously impressed; and head densely punctulate, sublucid to opaque. The relatively short eyes (worker REL ≤0.50, queen REL ≤0.48) and slender petiole (worker PLI ≤0.71, queen PLI ≤0.63) are also characteristic. Among the eight other major species groups of Pseudomyrmex (diagnosed in Ward, 1989) only the P. viduus and P. oculatus groups have workers and queens approaching these conditions. Those of the P. viduus group have a shinier head, a shorter and more robust petiole (worker PLI > 0.70, worker PWI > 0.70), and standing pilosity on the tibiae (reduced in one species), while workers and queens of the P. oculatus group have a palp formula of 6,3 (reduced to 5,3 only in smallest species with worker and queen HW <0.67), tectiform and sharp-edged median clypeal lobe with a broadly convex margin (dorsal view), elongate eyes (worker REL 0.48-0.61, worker REL 2 0.62-0.86, queen REL 0.43-0.57, queen REL 2 0.68- 0.89), and short petiole (worker PLI 0.67-1.06, queen PLI 0.57-0.94). Among taxonomically isolated species not belonging to one of the major species groups, P. fervidus (F. Smith) bears perhaps the closest phenetic resemblance to the P. ferrugineus group, but its workers and queens can be distinguished by their shinier and less densely punctulate head, shorter petiole (worker PLI 0.71- 0.76, worker PL/HL 0.41-0.44 (n=9); queen PLI≈0.65, queen PL/HL≈0.49), and standing pilosity on the outer faces of the tibiae. In addition the queens of P. fervidus have a distinctive, pointed median clypeal lobe not seen in P. ferrugineus group queens.
Males of the Pseudomyrmex ferrugineus group can be characterized by their palp formula, medially subangulate clypeal lobe, emarginate subgenital plate, configuration of the paramere, and shape of the aedaegus. They are approached most closely in this combination of traits by males of P. haytianus (Forel) and two undescribed Central American species (P. sp. PSW-02 and P. sp. PSW-54) although, curiously, the workers and queens of those species do not bear a close resemblance to those of the P. ferrugineus group.
All species in the P. ferrugineus group are obligate inhabitants of Central American swollen-thorn acacias, a biological trait not characterizing any other species group of Pseudomyrmex , although a few species in the otherwise quite different P. gracilis group and one species in the P. subtilissimus group have independently developed an obligate association with the acacias.
Distribution. - Members of the P. ferrugineus group are found from eastern (San Luis Potosi, Tamaulipas) and western (Sinaloa) Mexico south through Central America to northern Colombia (Fig. 67). Although no single species spans the entire range of the group, their collective distribution is virtually identical to that of the swollen-thom acacias (compare Fig. 67 with Janzen 1974:3).
Synonymic List of Species
P. ferrugineus (F. Smith 1877) Mexico to Honduras
= P. fulvescens (Emery 1890) (Ward 1989)
= P. canescens (Wasmann 1915) (Ward 1989)
= P. bequaerti (Wheeler 1942) (Ward 1989)
= P. sajfordi (Wheeler 1942) (Ward 1989)
= P. vesanus (Wheeler 1942) (Ward 1989)
= P. bequaerti (Enzmann 1945) (Brown 1949)
= P. honduranus (Enzmann 1945) (Ward 1989)
P.flavicornis (F. Smith 1877) Guatemala to Costa Rica
= P. belti (Emery 1890) (Ward 1989)
= P. obnubilus (Menozzi 1927a) (Ward 1989)
= P.fellosus (Wheeler 1942) (Ward 1989)
P. janzeni Ward , sp. nov. Mexico
P. mixtecus Ward , sp. nov. Mexico
P. nigrocinctus (Emery 1890) Guatemala to Costa Rica
= P. alfari (Forel 1906) syn. nov.
= P. bicinctus (Santschi 1922) syn. nov.
= P. peltatus (Menozzi 1927) syn. nov.
P. particeps Ward , sp. nov. Costa Rica
P. peperi (Forel 1913) Mexico to Nicaragua
= P. convarians (Forel 1913) (Ward 1989)
= P. sajfordi (Enzmann 1945) (Ward 1989)
= P. gaigei (Forel 1914) syn. nov.
= P. infemalis (Wheeler 1942) syn. nov.
= P. scelerosus (Wheeler 1942) syn. nov.
= P. infemalis (Enzmann 1945) (Brown 1949)
= P. scelerosus (Enzmann 1945) (Brown 1949)
P. satanicus (Wheeler 1942) Panama
P. veneficus (Wheeler 1942) Mexico
= P. venificus (Enzmann 1945) (Brown 1949)
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