Key to Malagasy Bothroponera wasmannii group workers

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This worker key and species group diagnosis is based on: Rakotonirina, J.C. & Fisher, B.L. 2013. Revision of the Pachycondyla wasmannii-group (Hymenoptera: Formicidae) from the Malagasy region. Zootaxa 3609, 101-141.

The following key also identifies ergatoid and winged queens to species as long as the form of the mesosoma and the presence of the mesopleural sulcus are not applied.

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

It should be noted that all diagnostic characters listed below are not unique to Malagasy P. wasmannii-group species but are shared with some Bothroponera (sensu Wheeler 1922) species from the Afrotropics.

1. Mandible subtriangular and robust, with masticatory margins bearing 7–9 teeth and denticles; groove running along the lateral portion from the base to the apex, but without a basilateral pit.

2. Palp formula 4,4.

3. Frontal lobes noticeably widely rounded anteriorly, the outer margins posteriorly narrow and compressed laterally at about the level of the eyes.

4. Clypeus usually with a truncate anteromedian margin, the shape of which is straight or slightly excised medially, but in P. tavaratra projects into a triangular lobe. The median portion posteriorly pinched into a slight triangle between the frontal lobes and extending backwards as a line at about the midlength of the head.

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

6. Compound eyes present and generally quite large but their maximum diameter less than the maximum width of the scape; posterior margin of the eye placed in the front of the midline of the head when viewed in profile.

7. Tibia of the hind legs with a pair of apical spurs, the posterior pectinate and the anterior smaller and simple.

8. Pretarsal claws generally simple, preapical tooth may be present at the base in larger species (P. comorensis, P. tavaratra).

9. Metanotal groove obsolete or lacking in the worker caste.

10. Mesopleural sulcus either clearly visible in P. masoala, P. wasmannii, and in some P. cambouei or indistinct in P. perroti, P. vazimba, and in some P. planicornis.

11. Propodeum generally broad in dorsal view, the rear margin rounded, not bidentate or bispinose.

12. Propodeal spiracle slit-like.

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

14. Basal fourth of all femora strongly laterally flattened.

15. Petiole nodiform, usually thick, tapered towards the apex in P. masoala.

16. Subpetiolar process hook-like anteriorly and with nearly flattened or very slightly convex surface; sometimes with transverse ridges in the posterior portion in P. comorensis, P. tavaratra, and in some P. cambouei.

17. Helcium almost on the anteroventral angle of the first gastral segment (abdominal segment IV).

18. Strong constriction between the first and second gastral segments.

19. Stridulitrum present.

20. Sting well developed.

21. Queen caste-specific characteristics: broader head, presence of ocelli, eyes larger 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 flattened anteroposteriorly relative to that of worker; somewhat larger body size with usually larger gaster and denser and more elongate pubescence.

In the Malagasy P. wasmannii-group species, the worker caste can generally be identified by the following character combination: mandibles without basi-lateral pit; obsolete metanotal groove; propodeal spiracle opening slit-shaped; hind leg with two tibial spurs, of which one is large and pectinate and the other smaller and simple; roughly basal fourth of all femora strongly laterally flattened; propodeal rear margin simple; petiolar node thick without spines on rear margin; and first and second gastral segments seperated by a strong constriction. In addition, the mesosoma and petiole node usually strongly sculptured, frontal lobes broadly rounded, and propodeal dorsum wide.

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1

  • Larger species (HW: 2.49–3.13 mm); with head in full-face view, antennal scape surpassing the posterior margin of the head (SI: 94–104) (Figs 1, 3); dorsum of head and mesosoma finely striate and interspersed with scattered punctures; dorsum of the body covered with erect stout hairs . . . . . 2
  • Smaller species (HW: 1.19–2.58 mm); with head in full-face view, antennal scape not surpassing the posterior margin of the head (SI: 70–87) (Fig. 2); dorsum of head and mesosoma variably sculptured but not finely striate, dorsum of the body with erect slender hairs and pubescence . . . . . 3

2

return to couplet #1

  • With head in full-face view, anterior margin of clypeus broadly rounded or medially triangular; eye breaking the outline of the side of the head (Fig. 3); hairs on the dorsum of the mesosoma and petiole node distinctly erect relative to the body surface . . . . . Bothroponera tavaratra
Pachycondyla tavaratra casent0410152 p 1 high.jpg
  • With head in full-face view, anterior margin of clypeus truncate; eye not breaking the outline of the side of the head (Fig. 4); hairs on the dorsum of the body decumbent and much more inclined to the body surface . . . . . Bothroponera comorensis
Pachycondyla comorensis casent0101553 profile 1.jpg

3

return to couplet #1

  • Basal half of the antennal scape dorsoventrally flattened, the leading edge very thin (Fig. 5); basitarsus of the hind leg laterally compressed, basal half of its inner surface concave . . . . . Bothroponera planicornis
Pachycondyla planicornis casent0096369 p 1 high.jpg
  • Basal half of the antennal scape subcylindrical, not dorsoventrally flattened; the leading edge rounded (Fig. 6); basitarsus of the hind leg generally rounded, without concavity . . . . . 4

4

return to couplet #3

  • With petiole in dorsal view, the node flattened, about twice as broad as long (Fig.7); higher than long in profile; erect hairs on dorsum of propodeum most frequently absent, if present then reduced in number . . . . . Bothroponera masoala
Pachycondyla masoala casent0317384 p 1 high.jpg
  • With petiole in dorsal view, the node thick, approximately as long as broad (Fig. 8), about as high as long in profile; erect hairs on dorsum of propodeum numerous or rarely absent . . . . . 5

5

return to couplet #4

  • Anterior half of the fourth abdominal tergite (gastral tergite 2) covered with numerous and very dense small punctures between larger ones (Fig. 9) which become moderate on mesosoma and petiole node; integument usually matte; mostly found in dry forest habitats . . . . . 6
  • Anterior half of the fourth abdominal tergite (gastral tergite 2) mostly smooth and shiny between large punctures, sometimes with randomly scattered small punctures (Fig. 10); mesosoma and petiole node sparsely punctulate between coarse punctae; integument mostly shiny; humid forest species . . . . . 7

6

return to couplet #5

  • Larger species (HW: 1.72–2.21 mm); mesopleural sulcus usually distinct and complete (Fig. 11); dorsum of mesosoma and petiole node covered with more robust and longer standing hairs; antennal segments 6, 7, and 8 nearly as wide as long; with petiole in dorsal view, the posterior margin straight or with weak median notch; outer surface of the hind tibia with erect hairs . . . . . Bothroponera wasmannii
Pachycondyla wasmannii casent0102409 profile 1.jpg
  • Smaller species (HW: 1.38–1.5 mm); mesopleural sulcus indistinct or incomplete (Fig. 12); dorsum of mesosoma and petiole node with short and thin erect hairs; antennal segments 6, 7, and 8 nearly twice as wide as long; with petiole in dorsal view, the posterior margin broadly concave; outer surface of the hind tibia usually without erect hairs . . . . . Bothroponera vazimba
Pachycondyla vazimba casent0486411 p 1 high.jpg

7

return to couplet #5

  • With mesosoma in profile, the dorsal outline forming a continuous convexity with a nearly rounded junction between the propodeal dorsum and the declivitous margin (Fig. 13), which is short and strongly inclined posteriorly; in full-face view, head heart-shaped, with the posterior margin strongly concave, and anterior clypeal margin strongly excised medially; larger species (HW: 2.34–2.58 mm) . . . . . Bothroponera perroti
Pachycondyla perroti admista casent0101035 profile 1.jpg
  • With mesosoma in profile, the dorsal outline not forming a continuous convexity, propodeal dorsum meeting the declivity at a distinct angle (Fig. 14); propodeal declivity nearly vertical, but not distinctly inclined posteriorly; in full-face view head not heart-shaped, the posterior margin usually straight or slightly concave; smaller species (HW< 2.3 mm) . . . . . Bothroponera cambouei
Pachycondyla cambouei blf2072(29)-12 profile 1.jpg