Streblognathus peetersi, Robertson, H. G., 2002

Robertson, H. G., 2002, Revision of the ant genus Streblognathus (Hymenoptera: Formicidae: Ponerinae)., Zootaxa 97, pp. 1-16 : 11-14

Streblognathus peetersi sp. nov.

Males from Natal described under S. aethiopicus by Emery (1899: 468).

Larvae from Natal described under S. aethiopicus by Wheeler and Wheeler (1989).

HOLOTYPE WORKER. Matching description of genus but with the following specimen-specific characters.

Size. Head width 3.87 mm; Head length 3.93 mm; Eye length 0.71 mm; Scape length 3.54 mm; Pronotal width 2.54 mm; Mesonotal-propodeal length 4.66 mm; Hind tibia length 4.04 mm; Cephalic index 99; Scape index 91; Eye index 18.

Head (Fig. 1a, b). Mandibles glossy smooth with sparsely distributed punctures containing hairs. Fringe of black hairs on anterior surface, behind basal margin and basal tooth. Anterior clypeal margin with middle section broadly concave, projecting beyond the outer margins and meeting them in a right angle. Compound eyes situated slightly anterior to mid-length of head. Fine puncturing on head poorly defined and smeared in appearance. Golden pubescence on head sparse to absent, limited mainly to the posterior, the central region and anterior to eyes. Antennal scapes with sparse golden pubescence overlaid by sparse decumbent black hairs. Venter of head smooth to shagreenate with sparse golden pubescence and uniformly distributed short, black hairs.

Mesosoma. Propodeal dorsum in profile mainly flat but curving down slightly to the metanotal groove and terminating posteriorly in dorsally projecting short spines (Fig. 1d).

Slight indentation present about one quarter of the way from the metanotal groove. No distinct lateral margins to propodeal dorsum. A hairless shallow furrow passes from the dorsal edge of the propodeal spiracle, round its posterior edge, and across to above the dorsal edge of the metapleural gland opening. Mesosoma dorsum covered in fine, ill-defined punctate sculpture, some of the punctures flowing into one another. Sides with shagreenate sculpture. Mesosoma covered in sparse, fine, golden pubescence and dorsum with scattered subdecumbent short, black, pointed hairs.

Petiole (Fig. 1d). Appearing as in description of genus. Covered in sparse golden pubescence and uniformly distributed subdecumbent short black hairs.

Gaster. As described for genus.

PARATYPE WORKERS. Matching the description of the genus and the holotype but with the following additional variation.

Size. Head width 3.83-4.12 mm; Head length 3.79-4.11 mm; Eye length 0.70-0.77 mm; Scape length 3.54-3.77 mm; Pronotal width 2.82-2.70 mm; Mesonotal-propodeal length 4.55-4.93 mm; Hind tibia length 3.91-4.26 mm; Cephalic index 98-102; Scape index 89-94; Eye index 18-19 (n=6).

ALL WORKERS.

Size. Head width 3.43-4.46 mm; Head length 3.60-4.50 mm; Eye length 0.62-0.85 mm; Scape length 3.28-4.12 mm; Pronotal width 2.30-2.84 mm; Mesonotal-propodeal length 4.34-5.47 mm; Hind tibia length 3.80-4.80 mm; Cephalic index 95-102; Scape index 87-98; Eye index 17-21 (n=38).

PARATYPE MALES.

Size. Head width 2.26-2.42 mm; Head length 1.83-1.90 mm; Eye length 1.25-1.32 mm; Ocellus diameter 0.55-0.69 mm; Forewing length 13.46-13.81 mm; Hind tibia length 4.02-4.12 mm; Cephalic index 122-128; Eye index 53-57 (n = 6).

ALL MALES.

Size. Head width 2.02-2.51 mm; Head length 1.62-1.97 mm; Eye length 1.12-1.41 mm; Ocellus diameter 0.42-0.69 mm; Forewing length 13.46-14.83 mm; Hind tibia length 3.83-4.38 mm; Cephalic index 121-130; Eye index 53-57 (n = 12).

Diagnosis. In the worker, scape, mesosoma and legs are shorter relative to width measurements in S. peetersi than in S. aethiopicus (Figs 5b, e, f), with scape index being the easiest measurement to separate the two species. The relatively longer body and appendages of S. aethiopicus , combined with its larger size results in Scape length, Meso-propodeal length and tibia length being longer in this species than in S. peetersi . There is also only a slight degree of overlap in Eye length (Fig. 5c). Mandibles in S. aethiopicus are castaneous with a black border whereas in S. peetersi they are generally black although there is a small proportion of specimens with some castaneous colouration.

In the male, the subgenital plate in S. peetersi has convex lateral margins and the apex is broadly rounded, whereas in S. aethiopicus the lateral margins are concave and the apex is flat (Figs 3c, d). The barbed apices of the penis valves are oriented vertically in S. peetersi whereas in S. aethiopicus , they splay outwards. In contrast, the barbs along the outer margins of the penis valves, behind the apices, are splayed outwards in S. peetersi whereas in S. aethiopicus they are oriented vertically.

Distribution and habitat. Streblognathus peetersi has a wide distribution in the grassland regions of eastern South Africa, Lesotho and Swaziland (Fig. 6).

Etymology. Named after Christian Peeters who drew my attention to this new species and collected the type material. It is also named after him in recognition of the substantial contribution he has made to our understanding of ponerine reproductive biology.

Type material examined. HOLOTYPE: worker, SOUTH AFRICA, Limpopo Province: next to Magoebaskloof Hotel , 23°53'S 29°59'E, 8.iv.2001, C. Peeters, SAM-HYM-C017887a ( SAMC). PARATYPE: workers (unless otherwise indicated): same locality as holotype, and collector is C. Peeters unless otherwise indicated: 24.i.2000, 'MAGOE #A', SAM-HYM-C015165 ; 24.i.2000, 'MAGOE#B', SAM-HYM-C015166 ; 24.i.2000, 'ZH-2', SAM-HYM-C015168 ; 24.i.2000, 'ZH-3', SAM-HYM-C015169 (males) ; 24.i.2000, SAM-HYM-C017879 ; 24.i.2000, 'ZH-1', SAM-HYM-C017880 ; v.2000, 'ZH-5', SAM-HYM-C017882 ; v.2000, 'ZH-6a', SAM-HYM-C017883 ; v.2000, 'ZH-7', SAM-HYM-C017884 ; J. de Oliveira, 9.ii.2001, 'ZH-9', SAM-HYM-C017885 ; J. de Oliveira, 10.ii.2001, 'ZH-10', SAM-HYM-C017886 ; 8.iv.2001, SAM-HYM-C017887 (workers and males) ( SAMC). Some duplicate specimens of above paratype material have been deposited in The Natural History Museum, London and at the California Academy of Sciences, San Francisco.

Additional material examined. LESOTHO: Bokong N.R. , 29°56'S 28°27'E, 29- 30.ix.1991, H. Geertsema ( SAMC) ; Haha-la-Sekhonyana , undetermined coordinates, 27.xii.1946, A. Jacot-Guillarmod ( AMGS) ; Katse (3 km SW of), 29°42'S 28°30'E, 21.i.1991, H. Geertsema ( SAMC) ; Likhoele , 29°11'S 27°19'E, no date, Dieterlin ( SAMC) ; Makheke Mnts 10 miles ENE Mokhotlong , No. 270 , 29°44'S 29°11'E, 9.iv.1951, P. Brinck & G. Rudebeck ( MZLU) ; Mamathes , 29°53'S 27°48'E, x.1957, Nat. Mus. S. Rhodesia ( SAMC) ; same locality but 29.ix.1957, C. Jacot-Guillarmod ( AMGS) ; same locality and collector but 28.xi.1953 ( AMGS) ; Mamohau , 29°53'S 28°30'E, 25- 30.iii.1991, H. Geertsema ( SAMC) ; Masite , 29°24'S 27°27'E, 31.i.1930, J. Hewitt ( AMGS) ; Mokhotlong, 7200 ft , 29°43'S 29°05'E, 6.iv.1951, P. Brinck & G. Rudebeck ( MZLU) ; Qachas Nek , 30°54'S 28°41'E, 13.i.1969, C. Jacot-Guillarmod ( AMGS) . SOUTH AFRICA, Eastern Cape: Queenstown to Jamestown , 31°30'S 26°42'E, 14.iv.1988, A.J. Prins, A. Prins ( SAMC) ; Rhodes , 30°12'S 27°58'E, 10.iii.1951, P. Brinck & G. Rudebeck ( MZLU) . Free State: Bethlehem , 28°46'S 28°18'E, iii.1918, C.P. van der Merwe ( SAMC) ; Clarens, Langkrans , 28°26'S 28°34'E, 25.xii.1976, C. Peeters ( SAMC) ; Golden Gate , 28°30'S 28°37'E, 13- 16.xii.1982, H.J. Greyling ( SAMC) . KwaZulu-Natal: Cathedral Peak area, Catchment XIV, 1920-1930m alt. , 28°00'S 29°12'E, 4.xii.1989, I. Pajor ( SAMC) ; Cathedral Peak area, catchment XV, 1950m , 28°00'S 29°12'E, 13.x.1989, I. Pajor ( SAMC) ; Champagne Castle , 29°53'S 29°23'E, iv.1965, B.V.W. ( SAMC) ; Clovelly Farm, c6 km from Underberg, Camp V6 , 29°11'S 29°32'E, 3.ii.2000, H.G. Robertson ( SAMC) ; Giant's Castle , 29°40'S 29°29'E, i.1983, C. Peeters ( SAMC) ; Impendle , 29°34'45"S 29°57'57"E, 12.x.1993, J. Kotze ( SAMC) ; Kloof , 29°13'S 30°50'E, 8.v.1915, H.W. Bell Marley ( SAMC) ; Krantz Kloof , 29°14'S 30°51'E, 1.x.1916, H.W. Bell Marley ( SAMC) ; Maqwaza [= Maquasa] , 27°19'S 32°08'E, xi.1915, H.W. Bell Marley ( SAMC) ; Mfongosi, Zululand , 28°18'S 30°48'E, xii.1911, W.E. Jones ( SAMC) ; 6 miles from Nkandla to Qudeni , 28°24'S 31°02'E, 26.i.1957, J.H. Grobler ( SAMC) ; Nongoma, Zululand , 27°06'S 31°39'E, 1923, C. Fuller ( SAMC) ; Nongomi , 27°06'S 31°39'E, 29.xi.1957, J.J. Nel ( SAMC) ; Ntendeka Forest Reserve, 27km E of Vryheid , 27°09'S 31°24'E, 7.x.1991, M.H. Villet ( SAMC) ; Qudeni , 28°20'S 30°52'E, 27.i.1957, J.H. Grobler ( SAMC) ; Underberg , 29°12'S 29°29'E, 6.i.1988, N.P. Hill ( SAMC) ; Vernon Crookes Nature Reserve, ZI3 , 30°16'S 30°35'E, 2.ii.2000, C. Peeters . Limpopo Province: Entabeni Forest Reserve , 22°04'S 30°21'E, xi.1978, G.L. Prinsloo ( SANC) ; Koedoes-Riv. , 23°26'S 30°09'E, xii.1902, H.G. Breyer ( TMSA) ; Shiluvane , 24°58'S 30°16'E, iii.1906, Junod ( TMSA) ; Tzaneen , 23°10'S 30°09'E, 26.xii.1991, A. Turner ( SAMC) . Mpumalanga: Barberton , 25°13'S 31°03'E, no date, H. Edwards ( SAMC) ; same locality but 23.xii.1927, J.S. Taylor ( AMGS) ; same locality but 11.iv.1927, J.S. Taylor ( AMGS) ; Marieps Mountain , 24°26'S 30°52'E, 15.iv.1948, G. van Son ( TMSA) ; Nelspruit, 2528DB , xii.1979, E. de Wet ( SAMC) ; Nelspruit, 2531DA , 11.iv.1982, M. Jansson ( SAMC) ; Nelspruit 2530BD , iv.1982, E. Anastassiades ( SAMC) ; Stentor Estate, Dist. Kaapmuiden , 25°23'S 31°23'E, 4.iv.1983, A. Nel ( SAMC) ; Uitsuk Forest Station , 25°45'S 30°44'E, 28.ix.1986, S. Endrody-Younga ( SAMC) . SWAZILAND: Piggspeak, Swaziland , 25°02'S 31°14'E, 18.vi.1987, J.A. Warrens ( SAMC) .

Discussion

There is quite extensive size variation in S. peetersi with the head width of the smallest measured worker only 77% of that in the largest worker whereas for S. aethiopicus it is 86%. Most of the size variation has a geographical basis, with workers in southern KwaZulu-Natal, Lesotho and Free State being smaller than those further north in northern KwaZulu-Natal, Swaziland, Mpumalanga and Limpopo Province.

The large, recurved barbs on the penis valves are possibly an adaptation for preventing easy removal of the genitalia after insemination. Monnin and Peeters (1998) showed in Dinoponera quadriceps , that a male did not withdraw his genitalia after insemination of a receptive worker, and instead the worker used her mandibles to cut off the genitalia from the male and then spent about 30 minutes removing the genitalia from inside herself. Once removed, she was no longer receptive to further mating by other males. The male genitalia in D. quadriceps therefore act as a mating plug, preventing further insemination by other males. As there is only one receptive 'alpha' worker per nest, who prevents mating by other workers, the reproductive interests of the male are best served by committing himself suicidally to a single mating, rather than withdrawing, exposing the receptive worker to mating by other males, and running the high risk of not locating another receptive worker at another nest. As Streblognathus is also monogynous, the recurved barbs on the male penis valves are probably also to secure the male genitalia in the worker's bursa copulatrix so that the genitalia act as a mating plug. The fact that the barbs in Streblognathus are so much larger than those in Dinoponera (personal observations), suggests that perhaps an even more persistent mating plug occurs in this genus.