Key to Malagasy Euponera sikorae species-group

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This worker key and group diagnostic section is based on: Rakotonirina, J.C. & Fisher, B.L. 2013. Revision of the Pachycondyla sikorae species-group (Hymenoptera: Formicidae) in Madagascar. Zootaxa 3683, 447-485.

Diagnosis of workers and queens of P. sikorae species-group

In the Malagasy region, the E. sikorae-group is most similar to species in the recently revised Bothroponera wasmannii-group (by Rakotonirina & Fisher 2013). These two groups share many characters listed below but the sikorae-group can be distinguished by the presence of a lateral circular pit at the base of the mandibles (Fig. 1). In the field, verification of the circular pit in the smaller species may be difficult, but workers of the E. sikorae-group can be recognized by their slender body, shiny integument, and their immediate moving reaction when their nests are disturbed. Conversely, those of the E. wasmannii-group can be identified by their robust body, matte integument, and their ability to simulate death when disturbed

1.Mandible subtriangular, masticatory margin with 9–12 teeth and denticles.

2.Mandible with dorsolateral pit or fovea near the base; lateral sulcus present, running from the base to the apex.

3.Palp formula 2, 2.

4.Frontal lobes with an anteriorly broadly rounded outer margin which is posteriorly and laterally compressed to form a narrow surface at about the level of the eyes.

5.Anteromedian margin of clypeus straight and medially notched in P. gorogota, P. haratsingy, P. ivolo, P. maeva, P. mialy, P. nosy, P. sikorae or triangular or broadly rounded in P. agnivo, P. antsiraka, P. daraina, P. rovana, P. tahary, P. vohitravo and P. zoro.

6.Antenna with 12 segments, the funiculus gradually increasing in width towards the apex and without a distinct club.

7.Compound eyes variable in size, rarely larger than the maximum diameter of antennal scape or greater (P. sikorae, P. agnivo) and most often smaller than approximately half of the maximum diameter of antennal scape; located roughly at the midline of the head when viewed in profile.

8.Apical portion of hind tibiae with two spurs, a large pectinate spur and an anterior spur that is much smaller and simple.

9.Pretarsal claws simple.

10.Metanotal groove strongly impressed in P. gorogota, P. maeva, and P. sikorae to feebly distinct in P. haratsingy and P. nosy, or absent in other remaining species.

11.Mesopleural sulcus usually indistinct, present as three to fourbroad, discontinuous grooves or as a single narrow sulcus.

12.Posterolateral margin of propodeum simply rounded or marginate (P. haratsingy, P. rovana, P. sikorae), bordered with lamellae (P. gorogota, P. maeva, P. daraina, P. zoro) or covered with a series of sharp teeth or denticles (P. antsiraka, P. tahary, P. vohitravo).

13.Propodeal spiracle slit-like.

14.Metapleural gland opening just above the posteroventral angle of mesosoma.

15.Petiole node usually thick, very rarely a flattened scale with slight posteromedian notch (P. gorogota, P. maeva).

16.Helcium approximately at the anteroventral angle of the first gastral segment (fourth abdominal segment).

17.First and second gastral segments with distinct constriction.

18.Stridulitrum absent.

19.Sting well developed.

20.Queen comparatively similar to worker, but with the following distinctive features: broader head, presence of ocelli, eye diameter greater than the greatest width of antennal scape; mesopleuron divided into an episternum and katepisternum by a transverse sulcus; the mesosomal flight sclerites fully developed; petiole node more or less flattened anteroposteriorly; moderately larger body size with usually more voluminous gaster and denser and more elongate pubescence.

The worker caste of the P. sikorae-group in Madagascar can be identified by the combination of the following characters: presence of a pit on the lateral portion of the base of the mandibles (Fig. 1); the shape of the anterior clypeal margin either approximately straight with slight median notch (Fig. 2) or projecting into triangular lobe (Fig. 3); the slit-shaped opening of propodeal spiracles; metanotal groove either present or absent; hind legs with two tibial spurs, of which one is large and pectinate and the other smaller and simple; posterior margin of propodeum simple, lamellate or infrequently with a series of sharp teeth; thick petiolar node whose posterodorsal angle has no long spines and whose posterolateral margins occasionally have a series of sharp teeth or tubercles (Fig. 19); the frontal lobes are broadly rounded. Workers of the P. sikorae-group are superficially similar to those of the P. wasmannii-group, but the former have a lateral circular pit or fovea near the base of their mandibles, which is absent in the P. wasmannii-group.

The shape of the anterior margin of the clypeus allows the division of the P. sikorae-group into two species complexes. First, the sikorae complex, which includes seven species, has a broadly transverse and roughly straight anterior clypeal margin, with slight median notch (Fig. 2); second the vohitravo complex, which also contains seven species, is characterized by a medially convex or bluntly angulate anterior margin of clypeus (Fig. 3).

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Euponera

The function of the key is primarily to identify workers, but can also identify ergatoid and winged queens to species as long as the shape of the mesosoma is not considered.

1

  • With head in full-face view, anterior margin of clypeus widely transverse and more or less straight, with weak median notch (Fig. 2) (sikorae complex) . . . . . 2
  • With head in full-face view, anterior margin of clypeus generally convex or medially bluntly angulate; slight median notch may be present (Fig. 3) (vohitravo complex) . . . . . 8
RFE01.jpg

2

return to couplet #1

  • Posterior surface of petiole node covered with numerous slender hairs and abundant pubescence; anterior surface of third abdominal segment concave, forming a shallow cavity to lodge the posterior surface of the petiole (Fig. 4) . . . . . 3
  • Posterior surface of petiole node convex and not covered with numerous slender hairs and abundant pubescence; anterior sur¬face of the third abdominal segment straight, without shallow cavity to lodge the posterior surface of the petiole (Fig. 5) . . . . . 4
RFE02.jpg

3

return to couplet #2

  • Lateral surface of head and petiole node smooth and shiny, with scattered piligerous punctures (Fig. 6) [known from queen specimen] . . . . . Euponera ivolo
  • Lateral portion of head densely and finely reticulate-rugulose, sides of petiolar node densely and finely punctate (Fig. 7) . . . . . Euponera haratsingy
RFE03.jpg

4

return to couplet #2

  • With mesosoma in dorsal view, metanotal groove deeply impressed (Fig. 8); in lateral view the dorsal outline of mesosoma complex, at least with distinct convex mesonotum . . . . . 5
  • With mesosoma in dorsal view, metanotal groove not impressed or absent (Fig. 9); in lateral view, the dorsal outline of mesosoma almost straight or slightly evenly convex, without breaks . . . . . 7
RFE04.jpg

5

return to couplet #4

  • Petiole node anteroposteriorly flattened in profile (Fig. 10), in dorsal view its posterior margin medially notched; posterior margin of head slightly concave; antennal scape not surpassing the concave posterior cephalic margin; mandible smooth between small punctures; tegument densely and finely reticulate-punctate . . . . . 6
  • Petiole node thick in profile (Fig. 11); in dorsal view, the posterior margin broadly convex; antennal scape surpassing the broadly convex posterior cephalic margin; mandible striate-punctate; black species with mostly smooth and shiny tegument . . . . . Euponera sikorae
RFE05.jpg

6

return to couplet #5

  • Posterolateral margin of propodeum bordered with broad lamellae which project as tubercles at about the level of propodeal spiracle; antennal scape and outer surface of each tibia covered with erect, slender hairs (Fig. 12); dorsum of head near the posterior margin and rest of body covered with numerous slender long hairs; posterior cephalic margin more or less straight . . . . . Euponera gorogota
  • Posterolateral margin of propodeum bordered with narrow lamellae which form an obtuse angle at about the level of propodeal spiracle; antennal scape and outer surface of each tibia lacking erect, slender hairs (Fig. 13); dorsum of head and rest of body covered with few erect, slender hairs; posterior cephalic margin concave . . . . . Euponera maeva
RFE06.jpg

7

return to couplet #4

  • Smaller species (HW: 1.15, HL< 1.5, WL: 1.78); eyes smaller, with seven to eight ommatidia; metanotal groove absent (Fig. 14); mesopleural suture lacking . . . . . Euponera mialy
  • Larger species (HW: 1.44, HL: 1.62, WL: 2.34); eyes larger, with 13 ommatidia; metanotal groove present as a dotted line (Fig. 15); mesopleural suture present . . . . . Euponera nosy
RFE07.jpg

8

return to couplet #1

  • Anterior surface of the third abdominal segment concave (Fig. 16), forming a shallow cavity to lodge the median portion of the posterior surface of petiole node . . . . . Euponera agnivo
  • Anterior surface of the third abdominal segment straight, not forming a shallow cavity to lodge the posterior surface of petiole node (Fig. 17) . . . . . 9
RFE08.jpg

9

return to couplet #8

  • Posterolateral margins of petiole node without a series of sharp teeth or tubercles (Fig. 18); dorsum of node not tubercuate . . . . . 10
  • Posterolateral margins of petiole node armed with a series of sharp teeth or tubercles (Fig. 19); dorsum of node tuberculate . . . . . 12
RFE09.jpg

10

return to couplet #9

  • In dorsal view, petiole node almost twice as broad as long (Fig. 20); in lateral view, subpetiolar process simple with only an anterior triangular lobe (Fig. 18) . . . . . Euponera daraina
  • In dorsal view, petiole nodenearly as broad as long (Fig. 21); in lateral view subpetiolar process with an anterior hook-like pro¬cess and a posterior subtriangular process separated by a concavity . . . . . 11
RFE10.jpg

11

return to couplet #10

  • Larger ant (HW: 1.22–1.32, WL: 1.85–2.05); mesopleuron and lower half of the side of propodeum mostly smooth and shiny with scattered small punctures in the center and fine rugulae at the junction of anepisternum and katepisternum and the lower portion of the metapleuron near the opening of the metapleural gland (Fig. 22) . . . . . Euponera zoro
  • Smaller species (HW: 1.01–1.14, WL: 1.58–1.77); mesopleuron and lower half of the side of propodeum densely rugulose and superimposed with punctures or foveolae (Fig. 23) . . . . . Euponera rovana
RFE11.jpg

12

return to couplet #9

  • Second gastral (fourth abdominal) tergite punctate to sparsely punctuate; pubescence absent or reduced in abundance on first and second gastral segments, distance between two adjacent pubescences generally equal to or greater than the length of the pubescence itself (Fig. 24) . . . . . 13
  • Second gastral (fourth abdominal) tergite densely punctate, with small punctures between larger ones; first and second gastral segments with abundant pubescence, distance between two adjacent pubescences always less than the length of the pubescence itself (Fig. 25) . . . . . Euponera vohitravo
RFE12.jpg

13

return to couplet #12

  • Mesopleural suture distinctly continuous and narrowly impressed (Fig. 26); head densely and finely reticulate-rugulose or reticulate-punctate behind the level of eye; with head in full-face view, the lateral borders at the level of anterior margin of eye not strongly curving towards the base of mandibles; in profile, distance between eyes and base of mandibles roughly three times or more than the maximum diameter of eye . . . . . Euponera antsiraka
  • Mesopleural suture indistinct, with broad and discontinuous concavities or impressions in this region, but no obvious suture (Fig. 27); head mostly smooth and shiny with faintly effaced reticulate-punctate sculpture behind the level of eyes; with head in full-face view, the lateral margins from the level of anterior margin of eye abruptly curving toward the base of mandibles; in lateral view, distance between eye and base of mandible slightly less than twice the maximum diameter of eye . . . . . Euponera tahary
RFE13.jpg