Key to Ocymyrmex

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Key to Ocymyrmex Workers. Based on: *Bolton, B. and A. C. Marsh. 1989. The Afrotropical thermophilic ant genus Ocymyrmex (Hymenoptera: Formicidae). Journal of Natural History. 23:1267-1308.PDF

The number of maxillary palp segments is very important in some key couplets. One or more specimens from any given series should be mounted with the mouthparts extended. In old specimens where the mouthparts are concealed the ant should be floated off its mount and relaxed, when the mouthparts can be extended and the palpi seen.

1

  • Mandible usually with only 4 teeth, rarely the third tooth with a minute denticle at its base. Only the third tooth (counting from the apical) paired internally on the masticatory margin. (South Africa) . . . . . Ocymyrmex gariepensis (this name is unavailable [1])
  • Mandible with 5 stout teeth. The third and fourth teeth (counting from the apical) paired internally on the masticatory margin . . . . . 2

2

3

  • With alitrunk in profile the propodeal outline rising steeply posteriorly, forming an elevated bluntly subconical peak at its junction with the declivity; entire dorsal outline of alitrunk strongly saddle-shaped. HW 1.06-1.18, SL 0.94-1.06, CI 105-108, SI 88-91. (South Africa) . . . . . . . . . . Ocymyrmex cavatodorsatus
Profile of Ocymyrmex cavatodorsatus worker
  • With alitrunk in profile the propodeal outline not rising posteriorly, not forming an elevated subconical peak at its junction with the declivity; entire dorsal outline of alitrunk not saddle-shaped. HW <0.95, SL<0.90, CI ca 100, SI ca 93. (South Africa) . . . . . . . . . . Ocymyrmex gordoni (this name is unavailable [2])

4

  • Anterior clypeal margin without a conspicuous semicircular to V -shaped median impression or notch, the margin entire and evenly convex, or at most somewhat flattened in the middle. . . . . . 5
  • Anterior clypeal margin with a semicircular to V-shaped median impression or notch, which is usually very conspicuous; the impression often flanked by a pair of dentiform prominences or distinct teeth. . . . . . 10

5

  • Smaller species, HW 1.25-1.28, SL 1.37-1.40. PW 0.75-0.80. With the head in full-face view the large eyes (0.26 x HW or more) very obviously breaking the outline of the sides. Middle of anterior clypeal margin rarely flattened, usually with a low broad bluntly triangular prominence. (Namibia) . . . . . Ocymyrmex turneri
Head of Ocymyrmex turneri worker
Profile of Ocymyrmex turneri worker
  • Much larger species, HW > 1.70, SL > 1.50, PW > 1.00. With the head in full-face view the smaller eyes ( < 0.25 x HW) usually just failing to break the outline of the sides. Middle of anterior clypeal margin always lacking a triangular prominence . . . . . 6

6

  • First gastral tergite in dorsal view strongly constricted basally and forming a narrow neck, the sclerite in this region roughly parallel-sided and no broader than the postpetiole. Petiole node low and broadly rounded in profile, with a blunt angular ventral process about halfway along the peduncle . . . . . 7
  • First gastral tergite in dorsal view not constricted basally, without a narrow neck, the sclerite broadening evenly from its articulation with the postpetiole. Petiole node high and domed in profile, without trace of a ventral process at the midlength of the peduncle. . . . . . 8

7

  • Metapleurallobes large and very strongly prominent, plainly visible in absolute profile, not concealed by the bulge of the metapleural gland bulla. HW 2.04, PW 1.30, CI 98. (Angola) . . . . . Ocymyrmex cursor
Head of Ocymyrmex cursor worker
Profile of Ocymyrmex cursor worker
  • Metapleurallobes very small, not prominent, scarcely or not visible in absolute profile, mostly or entirely concealed by the bulge of the metapleural gland bulla. HW 1.70-1.74, PW 1.08-1.14, CI 102-103. (Angola) . . . . . Ocymyrmex laticeps
Head of Ocymyrmex laticeps worker
Profile of Ocymyrmex laticeps worker

8

  • Basal half of first gastral tergite with numerous conspicuous hairs which are as long as those on the mesonotal and propodeal dorsa. Antennal scapes relatively long, SI > 110. Entire ant black to the naked eye, the gaster the same colour as the alitrunk. (Namibia) . . . . . Ocymyrmex zekhem
Head of Ocymyrmex zekhem worker
Profile of Ocymyrmex zekhem worker
  • Basal half of first gastral tergite without hairs or at most with a few inconspicuous hairs which are much shorter than those on the mesonotal or propodeal dorsa. Antennal scapes relatively short, SI < 110. Entire ant not black to the naked eye . . . . . 9

9

  • Head red, alitrunk duller red to black, gaster yellowish to black. Hairs on dorsal alitrunk usually white to silvery, only rarely coloured. SI 101-105, CI 95-97. (Angola, Namibia) . . . . . Ocymyrmex velox
Head of Ocymyrmex velox worker
Profile of Ocymyrmex velox worker
  • Colour everywhere a uniform rich orange-brown, or sometimes with the gaster slightly lighter. Hairs on dorsal alitrunk uniformly reddish brown. SI 94-102, CI 97-101. (Angola) . . . . . Ocymyrmex ankhu
Head of Ocymyrmex ankhu worker
Profile of Ocymyrmex ankhu worker

10

  • Large or very large species, HW > 2.00, SL > 1.90 . . . . . 11

11

  • Hairs on dorsal alitrunk dark reddish brown to blackish. Extremely large species, HW 2.30 or more. (Zimbabwe, Botswana, South Africa, Namibia, Angola) . . . . . Ocymyrmex picardi
Head of Ocymyrmex picardi worker
Profile of Ocymyrmex picardi worker
  • Hairs on dorsal alitrunk white to silvery. Large species but not approaching the above in size, HW in range 2.02-2.15. . . . . . 12

12

  • Dorsum of head behind level of eyes with dense tranverse costulate sculpture; groundsculpture between costulae vestigial. SI > 100. Mesothoracic spiracles with orifices protected by a pair of low tumuli or welts which project from the surface. Metapleurallobes slightly upcurved. (Somalia) . . . . . Ocymyrmex robecchii
Head of Ocymyrmex robecchii worker
Profile of Ocymyrmex robecchii worker
  • Dorsum of head behind level of eyes with dense, usually irregular, longitudinal rugular sculpture; ground-sculpture between rugulae conspicuous. SI usually < 100. Orifices of mesothoracic spiracles lacking protective low tumuli or welts projecting from the surface. Metapleural lobes not upcurved . . . . . 13

13

  • Petiole node in dorsal view flattened and its central portion strongly expanded laterally, the median section of the node projecting as a blunt triangular prominence on each side. (Botswana, South Africa) . . . . . Ocymyrmex alacer
Head of Ocymyrmex alacer worker
Profile of Ocymyrmex alacer worker
  • Petiole node in dorsal view rounded, its central portion not strongly expanded laterally; sides of node evenly shallowly convex and lacking blunt triangular prominences on each side. (Botswana, South Africa) . . . . . Ocymyrmex sphinx
Head of Ocymyrmex sphinx worker
Profile of Ocymyrmex sphinx worker

14

15

  • Alitrunk black. Head mostly dark reddish brown, but mandibles and head to level of frontal lobes lighter. Gaster blackish brown, intermediate in shade between head and alitrunk. Median clypeal impression a deep notch. HW 1.22-1.31, SL 1.30-1.40. (Namibia) . . . . . Ocymyrmex tachys
Head of Ocymyrmex tachys worker
Profile of Ocymyrmex tachys worker
  • Alitrunk red. Head unicolourous dull orange-red. Gaster blackish brown, much darker than both head and alitrunk. Median clypeal impression very shallow. HW 1.16-1.19, SL 1.23-1.26. (Namibia) . . . . . Ocymyrmex engytachys
Head of Ocymyrmex engytachys worker
Profile of Ocymyrmex engytachys worker

16

  • In profile the basal outline of the first gastral tergite and first sternite both convex from their articulation with the postpetiole, never with a neck-line or truncated-subconical outline basally. In dorsal view the first gastral tergite not constricted basally to form a narrow parallel-sided neck behind the postpetiole, the gaster broadening more or less evenly from immediately behind the postpetiole. . . . . . 17
  • In profile the basal outline of the first gastral tergite straight to very weakly convex, the first sternite straight to concave, from their articulation with the postpetiole; with a neck-like section or truncated narrowly subconical outline basally. In dorsal view the first gastral tergite constricted basally and forming a narrow, frequently parallel-sided, elongate neck immediately behind the postpetiole. . . . . . 22

17

  • Ventral surface of postpetiolar sternite transverse, or at most with a broad even and very shallow median longitudinal concavity. Cuticular flange of anterior clypeal margin very broad. Petiole node in profile never a high strongly sculptured dome . . . . . 18
  • Ventral surface of postpetiolar sternite with a deep median longitudinal groove or impression which divides the sclerite into a pair of roughly triangular projecting halves. Either cuticular flange of anterior clypeal margin a narrow strip, or petiole node in profile a high strongly sculptured dome, or both . . . . . 20

18

  • Larger species with relatively narrow head, dimensions in range HW 1.44-1.56, CI 87-91, SL 1.48-1.56, SI 100-104, PW 0.88-0.96. (Namibia) . . . . . Ocymyrmex kahas
Head of Ocymyrmex kahas worker
Profile of Ocymyrmex kahas worker
  • Smaller species with relatively broad head, dimensions in the range HW 1.24-1.36, CI ca 94, SL 1.20-1.34, SI 97-99, PW 0.78-0.84 . . . . . 19

19

  • Head a glossy dull red, remainder of body black. Petiole in profile with the peduncle grading into the node, the two not distinctly separable. (Namibia) . . . . . Ocymyrmex afradu
Head of Ocymyrmex afradu worker
Profile of Ocymyrmex afradu worker
  • Entirety of head and body yellow. Petiole in profile with the peduncle distinctly separated from the node. (Namibia) . . . . . Ocymyrmex flavescens

20

  • Dorsum of head with strongly developed rugular sculpture, usually dense and frequently irregular to vermiculate in places; head never with a slick glossy appearance, the sculpture always strong. Sides of petiole node with strong dense sharply defined vertical rugulose sculpture; in most individuals the rugulae also running across the dorsum of the node. (South Africa) (Workers of cilliei will also run out here; see notes under barbiger) . . . . . Ocymyrmex barbiger
Head of Ocymyrmex barbiger worker
Profile of Ocymyrmex barbiger worker
  • Dorsum of head with fine weak costulate to rugulose sculpture, often superficial; the head usually with a slick and glossy appearance, the sculpture always weak. Sides of petiole node granular or at most with extremely feeble vertical rugulae . . . . . 21

21

  • Costulae on sides of pronotum strongly developed but relatively sparse and widely separated, only about 12 (sometimes fewer) such costulae present at the pronotal midlength from its basal margin to the level of the base of the mesothoracic spiracle. Uniformly medium to light brown species. (South Africa, Namibia) . . . . . Ocymyrmex dekerus
Head of Ocymyrmex dekerus worker
Profile of Ocymyrmex dekerus worker
  • Costulae on sides of pronotum delicately developed but relatively dense and close-packed, with distinctly more than 12 such costulae (usually 18-20) present at the pronotal midlength from its basal margin to the level of the base of the mesothoracic spiracle. Not uniformly brown species. (Namibia) . . . . . Ocymyrmex robustior
Head of Ocymyrmex robustior worker
Profile of Ocymyrmex robustior worker

22

  • With alitrunk in dorsal view the metapleura and sides of the propodeum only sparsely clothed with hairs, or nearly hairless; at most with scattered short hairs which are mostly decumbent or subdecumbent; whole side of alitrunk lacking a densely hairy or furry aspect. Dorsum of alitrunk in profile weakly to moderately hairy but without a dense coat of short hairs between the longer main pilosity . . . . . 23
  • With alitrunk in dorsal view the metapleura and sides of the propodeum abundantly clothed with dense conspicuous outstanding pilosity; whole side of alitrunk with a densely hairy or even furry appearance. Dorsum of alitrunk in profile very densely hairy, usually with a dense coat of short hairs between the longer main pilosity. . . . . . 31

23

  • Sides of petiole node completely covered with dense strong, sometimes irregular, vertical rugulae or rugae. In dorsal view the rugulae seen to be continuous around the entire node, which thus appears encircled by coarse rugulae everywhere . . . . . 24
  • Sides of petiole node at most with a few weak to vestigial rugulae or rugular remnants; sometimes without rugulae. In dorsal view these feeble rugulae may persist, may fade out, or may be replaced entirely or in part by fine shagreening or granulation, but in no case does the entire node appear encircled with coarse dense rugulae everywhere. . . . . . 26

24

  • Petiole node in dorsal view broad, the length from the level of the spiracles to the apex posterior margin of the petiole less than 1• 30 times the maximum width of the node. Petiole node in profile with its posterior face abruptly descending, usually vertically. Alitrunk dark dull reddish brown to reddish black; gaster yellow to yellowish red; head dull red, intermediate in colour between that of alitrunk and gaster. (Zimbabwe, Botswana, South Africa) . . . . . Ocymyrmex sobek
Head of Ocymyrmex sobek worker
Profile of Ocymyrmex sobek worker
  • Petiole node in dorsal view narrow, the length from the level of the spiracles to the posterior margin of the petiole greater than 1•40 times the maximum width of the node. Petiole node in profile with its posterior face usually conspicuously sloping. Colour not as above, either uniformly orange-red to dull red throughout, or with the gaster much darker than the head. . . . . . 25

25

  • Petiole node in profile large and massively developed. Entire ant orange-red to dull red throughout, sometimes the gaster slightly lighter in shade than the head. (Zimbabwe, South Africa) . . . . . Ocymyrmex foreli
Head of Ocymyrmex foreli worker
Profile of Ocymyrmex foreli worker
  • Petiole node in profile small and not massively developed. Head dull red, alitrunk the same colour or darker, gaster black. (Kenya, Tanzania) . . . . . Ocymyrmex phraxus
Head of Ocymyrmex phraxus worker
Profile of Ocymyrmex phraxus worker

26

  • Dorsum of head behind a line connecting anterior margins of eyes to posteriormost point of frontal lobes either finely regularly costulate or almost smooth. When costulae distinct the sculpture is fine, very regular and parallel everywhere, without trace of irregular, vermiculate areas, blanketing coarse punctation or granular sculpture, or areas of chaotic sculpture. When almost smooth the surface showing only faint to vestigial costulae on a very glossy surface . . . . . 27
  • Dorsum of head behind a line connecting anterior margins of eyes to posteriormost point of frontal lobes never finely regularly costulate, never almost smooth. Instead the sculpture always strong and including either distinctly irregular rugulae, vermiculate areas, blanketing coarse punctate or granular sculpture, or areas of chaotic sculpture. . . . . . 29

27

  • Costulae on dorsum of head strongly and evenly developed everywhere, usually strikingly parallel from front to back across the entire surface, the cephalic dorsum without a slick, polished or wet-looking appearance. (Zambia, Zimbabwe, Botswana, South Africa, Namibia, Angola) . . . . . Ocymyrmex fortior
Head of Ocymyrmex fortior worker
Profile of Ocymyrmex fortior worker
  • Costulae on dorsum of head weakly or sometimes unevenly developed, often superficial to vestigial and may even be absent in places; the cephalic dorsum always with a slick, polished or wet-looking appearance . . . . . 28

28

  • Pronotum in profile with dorsal outline more or less flat or even slightly concave. Head somewhat longer and narrower, CI 92-93. (Sudan, Kenya) . . . . . Ocymyrmex celer
Head of Ocymyrmex celer worker
Profile of Ocymyrmex celer worker
  • Pronotum in profile with dorsal outline evenly convex. Head somewhat broader, CI 96-100. (Ethiopia, Somalia, Kenya, Uganda, Tanzania) . . . . . Ocymyrmex nitidulus
Head of Ocymyrmex nitidulus worker
Profile of Ocymyrmex nitidulus worker

29

  • Petiole node elongate, narrow and longitudinal in dorsal view, the node as long as or longer than broad and the posterior peduncle only very slightly narrower than the node itself. Postpetiole in dorsal view as long as broad to longer than broad. (Angola, Namibia) . . . . . Ocymyrmex monardi
Head of Ocymyrmex monardi worker
Profile of Ocymyrmex monardi worker
  • Petiole node short, broad and transverse in dorsal view, the node distinctly broader than long and the posterior peduncle conspicuously much narrower than the node. Postpietole in dorsal view usually obviously broader than long but sometimes only slightly so . . . . . 30

30

  • Gaster much lighter in colour than alitrunk. Sculpture of cephalic dorsum near inner margin of eye minutely vermiculate and chaotic, without a distinct longitudinal direction. Rugulae on sides of pronotum fine, dense and closely packed. (Namibia) . . . . . Ocymyrmex okys
Head of Ocymyrmex okys worker
Profile of Ocymyrmex okys worker
  • Gaster darker in colour than alitrunk. Sculpture of cephalic dorsum near inner margin of eye strongly rugulose and with a marked longitudinal direction. Rugulae on sides of pronotum strongly developed but widely spaced. (South Africa, Lesotho) . . . . . Ocymyrmex weitzeckeri
Head of Ocymyrmex weitzeckeri worker
Profile of Ocymyrmex weitzeckeri worker

31

  • With alitrunk in profile the pronotum and anterior mesonotum forming a high and narrow dome-like convexity. (Namibia) . . . . . Ocymyrmex shushan
Head of Ocymyrmex shushan worker
Profile of Ocymyrmex shushan worker
  • With alitrunk in profile the pronotum and anterior mesonotum forming an even shallow low broad convexity, or the pronotum more or less flat and sloping upwards posteriorly. . . . . . 32

32

  • In dorsal view the first gastral tergite at least as broad as long, the maximum mid-dorsal length equal to or less than the maximum width of the sclerite. Basally the first gastral tergite with a short parallel-sided narrow neck, behind which the sides are strongly convex-divergent. Body colour orange to orange-red. (Namibia) . . . . . Ocymyrmex micans
Head of Ocymyrmex micans worker
Profile of Ocymyrmex micans worker
  • In dorsal view the first gastral tergite much longer than broad, the maximum mid-dorsal length distinctly greater than the maximum width of the sclerite. Basally the first gastral tergite with a narrow neck whose sides diverge posteriorly, the sides contiguous with the sides of the remainder of the sclerite. Body colour usually much darker than the above, but not always so . . . . . 33

33

  • In full-face view most or all workers in any given series with a posteriorly arched to transverse band of very irregular to vermiculate fine dense but strongly developed rugulae on the vertex, between or behind the eyes. Less commonly this area with a chaotic mass of vermiculate rugulae without a discernible direction, or extremely rarely the vermiculate rugulae with a longitudinal trend. (Botswana, South Africa) . . . . . Ocymyrmex hirsutus
Head of Ocymyrmex hirsutus worker
Profile of Ocymyrmex hirsutus worker
  • In full-face view all workers with longitudinal and usually irregular fine dense rugulae on the vertex between and behind the eyes. If a small patch of transverse sculpture appears it is U-shaped and situated medially at the extreme occipital margin. . . . . . 34

34

  • Gaster dark, darker than the head, usually black or nearly so. Head and alitrunk dark red to blackish red. (South Africa) . . . . . Ocymyrmex ignotus
Head of Ocymyrmex ignotus worker
Profile of Ocymyrmex ignotus worker
  • Gaster yellow to dirty orange-yellow, lighter than the head. Head and alitrunk yellowish orange to dull red. . . . . . 35

35

  • Petiolar peduncle relatively short and stout in profile, suddenly narrowing anteriorly to its articulation with the alitrunk, its ventral margin sharply deflected upwards. In dorsal view petiole node short and broad, usually very much broader than long. (Botswana, South Africa, Namibia) . . . . . Ocymyrmex flaviventris
Head of Ocymyrmex flaviventris worker
Profile of Ocymyrmex flaviventris worker
  • Petiolar peduncle relatively long and narrow in profile, gradually narrowing anteriorly to its articulation with the alitrunk, its ventral margin not sharply deflected upwards. In dorsal view petiole node relatively elongate and narrow, usually about as long as broad, more rarely somewhat broader than long. (South Africa) . . . . . Ocymyrmex resekhes
Head of Ocymyrmex resekhes worker
Profile of Ocymyrmex resekhes worker