Key to Australian Polyrhachis (Campomyrma) species

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The following key to Australian Polyrhachis (Campomyrma) species (based on the worker caste) is currently incomplete. It contains keys for the gravis and micans groups (Kohout, 2013[1]) and the hexacantha complex (Kohout, 2012[2]).


Key to workers of P. gravis group

1

  • Dorsum of petiole armed with single spine => 2
  • Dorsum of petiole armed with pair of spines => 3

2

  • Pronotal humeri simply angular; eyes smaller, distinctly convex; dorsal petiolar spine long and acute (Fig. 5B,E-F) => Polyrhachis pseudothrinax
  • Pronotal humeri produced into short, distinct teeth; eyes larger, only moderately convex; dorsal petiolar spine short and blunt (Fig. 5D,G-H) => Polyrhachis unicornis

3

  • Petiolar node in profile distinctly swollen at base (Fig. 1F) => Polyrhachis bispinosa
  • Petiolar node in profile slender, scale-like (e.g. Figs 1H; 3H) => 4

4

  • Pilosity generally long, hair-like, rather abundant => 5
  • Pilosity generally short, bristle-like, less abundant => 6

5

  • Large species (HL 2.68); pilosity very long, abundant; lateral margins of propodeal dorsum barrel-shaped (VIC) => Polyrhachis captiva
  • Smaller species (HL < 2.50); pilosity shorter, more sparse, notably on dorsum of mesosoma; lateral margins of propodeal dorsum converging posteriorly (WA) => Polyrhachis capillata

6

  • Petiole high and slender in frontal view; dorsolateral margins steeply raised, strongly converging dorsally, forming single base for two slender dorsal spines (Fig. 4D,G); body black, somewhat semi-polished, with appendages light orange (WA, Kimberley) => Polyrhachis palmerae
  • Petiole about as long as wide in frontal view; dorsolateral margins less steep and less strongly converging dorsally; bases of dorsal pair of spines more widely separated (e.g. Figs 2D; 4B); body rather dull black, opaque, with appendages black or dark reddish-brown => 7

7

  • Dorsal petiolar spines tooth-like, distinctly shorter and stouter than lateral spines (Fig. 2D); bristle-like pubescence very sparse, virtually lacking from dorsum of mesosoma and petiole => Polyrhachis curtospinosa
  • Dorsal petiolar spines slender, distinctly longer than lateral spines (e.g. Figs 3B,D; 4B); bristle-like pubescence present on most body surfaces, including dorsum of mesosoma and petiole => 8

8

  • Anterior margin of first gastral tergite with strongly raised carina => 9
  • Anterior margin of first gastral tergite with only poorly indicated carina (WA) => Polyrhachis opacita

9

  • Antennal scapes longer (SI >125); eyes more-or-less normal, moderately convex; pronotal humeri narrowly rounded with pronotal margins behind shallowly emarginated; greatest width of pronotal dorsum at middle of segment (NT, QLD) => Polyrhachis gravis
  • Antennal scapes shorter (SI 115); eyes distinctly smaller, strongly convex; pronotal humeri distinctly angular; greatest width of pronotal dorsum across humeri (WA) => Polyrhachis hespera


Key to workers of P. hexacantha complex

1

  • Smaller species (HL < 1.81); lateral petiolar spines only weakly divergent in dorsal view, forming a continuous line with sides of petiolar node (Fig.

2) => Polyrhachis smithersi

  • Larger species (HL > 1.95); lateral petiolar spines widely divergent, strongly extending laterally before curving posteriorly (e.g. Fig. 9) => 2

2

3

  • Dorsum of mesosoma very finely and somewhat longitudinally striate; sculpturation of head distinctly finer, semipolished; intercalary spines of petiole only moderately long (Figs 6-7) => Polyrhachis fuscipes
  • Dorsum of mesosoma regularly reticulate-punctate, opaque; intercalary spines of petiole distinctly longer (Figs 9, 11-12) => Polyrhachis hexacantha


Key to workers of P. micans group

1

  • Petiole with four, almost subequal spines => 2
  • Petiole with two large dorsal spines; lateral spines greatly reduced or obsolete => 3

2

  • Petiole with dorsal margin strongly raised dorsomedially towards closely approximated dorsal spines (Fig. 6B, E); propodeal teeth rather massive, long and broad (Fig. 46); legs medium reddish-brown => Polyrhachis eureka
  • Petiole with dorsal margin less strongly raised; dorsal spines situated further apart (Fig. 7B); propodeal spines relatively short, more acute and slender (Fig. 7F); legs very dark reddish-brown or black => Polyrhachis micans

3

  • Body distinctly reddish-brown; lateral petiolar spines reduced to short acute teeth (NT, QLD) => Polyrhachis incerta
  • Body uniformly black; lateral petiolar spines reduced to blunt angles, or obsolete => 3

4

  • Propodeal dorsum very narrow, about 1.5 times longer than basal width, with parallel lateral margins; dorsal petiolar spines long and slender (WA, NT, QLD) => Polyrhachis prometheus
  • Propodeal dorsum distinctly wider than long, with strongly posteriorly converging lateral margins; dorsal petiolar spines relatively short (QLD) => Polyrhachis shattucki

References

  1. Kohout, R.J. 2013. A review of the Polyrhachis gravis and micans species-groups of the subgenus Campomyrma Wheeler (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum, Nature 56, 92-117.
  2. Kohout, R. 2012. A new species of the subgenus Campomyrma Wheeler of the genus Polyrhachis Fr. Smith from the Australian Capital Territory (Hymenoptera: Formicidae: Formicinae). Australian Entomologist 39, 321-329.