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Key to males of the obligate acacia-ants, Pseudomyrmex ferrugineus group

Although isolated acacia-ant males are unlikely to be encountered, the following key is offered as a supplement for determination of species in the P. ferrugineus group. It can be used to confirm worker- or queen-based identifications, but some couplets require examination of the male genitalia.

  1. Posterior margin of subgenital plate (sternite IX) with a shallow (less than semicircular) concavity (Fig. 54); scape short, SI2 0.33-0.43, SL/HL <= 0.21…2
    Posterior margin of subgenital plate (sternite IX) with a deep, semicircular concavity (Fig. 55); scape longer, SI2 0.43-0.56, SL/HL >= 0.22 …. 3
  2. Paramere, in lateral view, with a slender finger-like mediodorsal lobe and angulate posteroventral corner (Fig. 57)… particeps Ward
    Paramere, in lateral view, with a stubbier mediodorsal lobe and more gently rounded posteroventral corner (Fig. 56) …. nigrocinctus (Emery)
  3. Scape and compound eye longer, relative to HW (SI 0.29-0.35, REL2 0.56-0.62 (n=6)); head narrower, CI 0.82-0.94, HW 0.81-0.95; lateral view of paramere as in Fig. 58apeperi (Forel)
    Scape and compound eye shorter (SI 0.22-0.30, REL2 0.49-0.58); head broader, CI >= 0.94 and/or HW >= 0.96; lateral view of paramere not as in Fig. 58a…. 4
  4. Paramere, in lateral view, with posterodorsal corner well separated from mediodorsal lobe (Fig. 59a, Fig. 60a)…5
    Paramere, in lateral view, with posterodorsal corner bent upward and enclosing a space between itself and the mediodorsal lobe which is subequal to the area of the latter (Fig. 61a, Fig. 63a) …. 6
  5. Lateral view of paramere as in Fig. 59a: mediodorsal lobe relatively broad and partly enclosing a space between itself and the posterodorsal corner; larger species, HW 1.06-1.09 (n=5)…satanicus (Wheeler)
    Paramere typically as in Fig. 60a, with mediodorsal lobe more slender and more distant from posterodorsal corner (Fig. 60b depicts a less typical male, from Colombia); smaller species, HW 0.92-1.05 (n=12) …. spinicola (Emery)
  6. Mediodorsal lobe of paramere stout, directed more or less dorsally (Fig. 61a)…7
    Mediodorsal lobe of paramere more slender and directed posterodorsally (Fig. 63a) …. 8
  7. Body pubescence dense and conspicuous, suberect on dorsum of head, propodeum and petiole; smaller species, HW 0.79-0.88 (n=7)…veneficus (Wheeler)
    Body pubescence less dense and less conspicuous, predominantly appressed or decumbent on the propodeum and petiole; larger species, HW 0.88-0.97 (n=6) …. mixtecus Ward
  8. Smaller species, HW 0.93-0.96 (n=6)… janzeni Ward
    Larger species, HW 0.99-1.19 (n=22) …. ferrugineus (F. Smith) and  flavicornis (F. Smith)

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