Oxystigma cyanofrons Williamson 1919

Garrison, Rosser W., 2014, Review of Oxystigma Selys with the synonymy of Oxystigma williamsoni Geijskes (Odonata: Heteragrionidae), Zootaxa 3780 (2), pp. 347-364 : 358-359

Oxystigma cyanofrons Williamson 1919

Figs. 2–5 (head), 17–20 (thx), 27–30 (setifer), 35–36 (wing base) 43, 49–51 (app), 58 (map)

Oxystigma cyanofrons Williamson, 1919: 58 (description, illustration ♂, Tumatumari, British Guiana [now Guyana]), in UMMZ [examined]);— Geijskes 1943:165 (larva described under the name O. petiolatum );— Rácenis 1959: 365 (key);— Geijskes 1976: 216, 226 (key, treatment of species, diagnostic illustrations);— Davies & Tobin 1984: 42 (catalog, incorrectly cited as type species of Oxystigma );— De Marmels 1989: 19 (list);— De Marmels 1990: 335 (checklist);— Bridges 1994: VII.40 (catalog);— Steinmann 1997:156 (catalog);— Tsuda 2000: 70 (catalog); — Belle 2002: 2 (listed from Suriname);— Garrison et al. 2003: 14 (type catalog data);— Machet 2004: 35 ( French Guiana);—Machet in Meurgey et al. 2006: 35 ( French Guiana);— Heckman 2008: 298 (key to species); Garrison et al. 2010: 99 –100 (list).

Types. Holotype ♂: BRITISH GUIANA [now GUYANA]: Tumatumari, 5 Feb. 1912, L. A. & E. B. Williamson & B. J. Rainey leg., in UMMZ [examined; Garrison et al. 2003:14]

Specimens examined. Total: 15 ♂, 4 ♀. FRENCH GUIANA: Approuague-Kaw, Kaw Mountain, 104; malaise trap, FRG MF3, 4.5506°, W 52.1944°, 100m, 12 Feb. 2007, N. Jönsson leg., 1♂, 1♀ (RWG ex RH); SURINAME: Para Distr., Boven, RMNH.INS.512309 {N 5.36°, W 55.53°}, 35m, 13 Feb. 1960, J. Belle leg., 1♂ (RMNH); Brokopondo Distr., Compagnie Kreek RMNH.INS 512272 {N 5.13°, W 54.98°}, 15m, 19 Dec. 1965, J. Belle leg., 1♂ (RMNH); Taparoepa kreek, Brokopondo RMNH.INS.512274, 512291, 512311 {N 5.02°, W 54.99°}, 19m, 8 Mar. 1966, [no collector given], 3♂ (RMNH); Affobakka, river, RMNH.INS.512273 {N 5.0°, W 54.98°}, 52m, 27 May, 1959, J. Belle leg., 1♂ (RMNH); Sara kreek, Langetabbetje, RMNH.INS.512327 {N 5.0°, W 54.52°}, 81m, 13 Dec. 1965, [no collector given], 1♀ (RMNH); Brownsberg, Waktibasoe kreek, RMNH.INS.512419 {N 4.93°, W 55.12°}, 43m, 10 Aug. 1958, D. Geijskes leg., 1♂ (RMNH); Käyser Vliegveld, RMNH.INS.512343, {N 4.45°, W 54.43°}, 30m, Sept. 1960, Beatty leg., 1♂ (RMNH); Sipaliwini Distr., Boschpad bij Makambi kreek, RMNH.INS.512292 {N 4.90°, W 55.14°}, 43m, 22 Sept. 1938, D. Geijskes leg., 1♂ (RMNH); Paloemeu Joeloe, RMNH.INS.511813, {N 2.44°, W 55.47°}, 9 Jan. 1941, L. Schmidt leg., 1♂ (RMNH); Suriname Distr., Blanche Marie, val achter kamp, RMNH.INS.512289 {N 4.73°, W 56.88°}, 102m, 11 Feb. 1971, D. Geijskes leg., 1♂ (RMNH); GUYANA: Aramantani Creek, Dubulay Ranch {N 5.66°, W 57.92°}, 37m, 17 April 1995, O.S. Flint, Jr. leg. 1♂ (RWG ex USNM); BRAZIL: Amazonas State, Reserva Campinas, 60 km north of Manaus {S 2.40°, W 59.85°}, 100m, 6 Feb. 1979, O.S. Flint, Jr. leg. 1♂ (RWG ex USNM); Igarape Tarumanzinho, 46 km N Manaus {S 2.59°, W 60.03°}, 70m, 6 Feb. 1979, O.S. Flint, Jr. leg. 1♂ (RWG ex USNM); Reserva Ducke, 26 km E Manaus {S 3.00°, W 59.94°}, 120m, 2–4 Feb. 1979, O.S. Flint, Jr. leg. 1♀ (RWG ex USNM).

Diagnosis. Blue labrum, clypeus, and frons in mature (and well-preserved) males ( Fig. 3 ) easily distinguish this species from the closely related O. petiolatum where these structures are dark or obscured ( Figs. 6–14 ). The thoracic dorsum (mesepisterna) is largely all dark in O. cyanofrons , Figs. 17–18 (with pale areas along middorsal carina and bordering humeral suture in O. petiolatum , Figs. 21–23 ). However, in poorly preserved specimens, these differences can be difficult to use in discriminating between the two species ( Fig. 2 [ O. cyanofrons ] vs. Figs. 9, 11– 12, 14 [ O. petiolatum ]). For example, two males of O. petiolatum ( Figs. 11–12 ) have a pale coloration similar to that for O. cyanofrons except that the postclypeus is dark and the pale areas are cream instead of blue. One male of O. petiolatum ( Fig. 14 ) was labeled by Geijskes as O. williamsoni with a note "labrum pale or juv[enile]?" Variability in thoracic coloration noted above suggests caution when using this character in diagnosing O. cyanofrons from O. petiolatum .

Cerci in males of O. cyanofrons closely approach those for O. petiolatum . Their differences are subtle but seem to be consistent and correlate with the facial differences noted above that have traditionally been used to discriminate between these two species. The transverse ridge in O. cyanofrons is prominent and, when viewed dorsally, does not extend beyond the widest portion of the medial lobe ( Figs. 49 a–51a); the ridge in O. petiolatum extends more posteriorly in relation to its medial lobe ( Figs. 52 a–55a) or, in more southerly populations ( Figs. 56 a– 57a) ends before the widest portion of the medial lobe as in O. cyanofrons . However, the ridge in O. petiolatum from these more southerly populations ( Ecuador, Fig. 57 b; Rondônia State, Brazil, Fig. 56 b) is not prominent and disappears posteriorly, while in O. cyanofrons the ridge is prominent (49b–51b). A more subtle but consistent difference involves the juncture of the transverse ridge to the medial portion of the cercus. The difference, best seen in a postero-mesal view, show a pronounced v -shaped concavity where the transverse ridge meets its base ( Figs. 49 b–51b); in O. petiolatum , the juncture forms a shallow concavity ( Figs. 52 b–55b), the demarcation between transverse ridge and cercus is not so pronounced. Both of these characters seem to work well in zones of sympatry between O. cyanofrons and O. petiolatum but are less apparent in allopatric southerly populations of O. petiolatum ( Figs. 56 b–57b).

Female is unique by acute tip of the anteriorly curved setifer ( Figs. 27–30 ).

Remarks. Marcel Wasscher (pers. comm. 2013) provided the following notes for both O. cyanofrons and O. petiolatum in Suriname as follows: " Oxystigma cyanofrons quite rare in rather fast-flowing streams in forests of hilly and mountainous areas in the interior; Oxystigma petiolatum relatively common along slow-flowing creeks in the interior and locally on creeks in the savanna belt and coastal area."

Distribution. This species occurs in the Guyanas with a record of a single female from southern Venezuela (Amazonas State: Uruyén [foot of Auyán-Tepuí]) south through central Amazonas State, Brazil. It is sympatric with O. petiolatum with examples of both species being collected together; however, O. cyanofrons is less commonly represented in collections compared to O. petiolatum . De Marmels (pers. comm. 2013) kindly provided the following additional Venezuelan records (and approximate decimal coordinates) based on the results of my paper: Bolívar State: Bochinche, N 7.53º, W 60.67º; San Francisco de Las Babas, (above Salto Las Babas, on the other side of the river from Canaima), N 6.50º, W 62.90º; Canaima, N 6.23º, W 62.83º; Las Claritas, N 6.18º, W 61.31º; km 85 El Dorado-Santa Elena de Uairén, N 6.54º, W 61.57º (all MIZA).

Figures

FIGURES 1 – 8. Head, anterior (frontal) view.

FIGURES 17 – 24. Thorax latero-dorsal view.

FIGURES 9 – 16. Head, anterior (frontal) view (continued); 15 – 16. thorax dorsolateral view.

FIGURES 49 – 57. Right male cercus, dorsal view (A), postero-mesal view (B)

FIGURES 25 – 34. Female intersternite and setifer (mesopresternum), left lateral view.