Isoplenodia arabukoensis, Sihvonen, Pasi & Staude, Hermann S., 2010

Sihvonen, Pasi & Staude, Hermann S., 2010, Revision of Isoplenodia Prout, 1932 with new records from continental Africa (Lepidoptera: Geometridae, Sterrhinae), Zootaxa 2453, pp. 25-41 : 34-37

Isoplenodia arabukoensis sp. n. Sihvonen & Staude

Figs. 7, 8 , 18–20 , 27–29

Material Examined. Holotype: 3, labelled: “ HOLOTYPE / Isoplenodia arabukoensis / Sihvonen & Staude [red rectangular label]; Kenya, Gedi, Arabuko / Sokoke Forest Reserve, / mixed sand forest, / 50m, 3°20'S / 39°57'E, / 21-07-2002, H. S. / Staude; Genitalia prep. / No. 1329 / Pasi Sihvonen [blue rectangular label); [in TMP]”. Paratypes: 1 3 5 Ƥ, labelled: " PARATYPE / Isoplenodia arabukoensis / Sihvonen & Staude [yellow rectangular label]; Kenya, Gedi, Arabuko / Sokoke Forest Reserve, / mixed sand forest, / 50m, 3°20'S / 39°57'E, / 21-07-2002, H. S. / Staude; Genitalia prep. / No. 1327 / Pasi Sihvonen [blue rectangular label]", " PARATYPE / Isoplenodia arabukoensis / Sihvonen & Staude [yellow rectangular label]; Kenya, Gedi, Arabuko / Sokoke Forest Reserve, / mixed sand forest, / 50m, 3°20'S / 39°57'E, / 21-07-2002, H. S. / Staude; Genitalia prep. / No. 1328 / Pasi Sihvonen [blue rectangular label]". Paratypes are in HSS. Other specimens: 1 3: "Aberfoyle / Honde Valley [18°25´S, 32°53´E] / ZIMBABWE / 0 1 / [in the label] 10 / [in the label] [19] 94 / N J Duke [in TMP]"; 1 3: "ABERFOYLE / HONDE VALLEY / ZIMBABWE / 18.10.[19] 90 / N J Duke [in TMP]"; 1 male: Vumba [forest][19°03´S, 32°46´E] / S. Rhodesia [ Zimbabwe] / 10-5-75 / N. J. Duke; [in TMP]"; 2 3: " Rwanda, South Western, / Nyungwe Forest Reserve, / Uwinka, / 02°28'44''S / [in the label] 29°12'09''E / 2450m, / 20–23 / [in the label] 6 / [in the label] 2009 / H. S. Staude [in HSS]"; 1 Ƥ: " Rwanda, South Western, / Nyungwe Forest Reserve, / Uwinka, / 02°28'44''S / [in the label] 29°12'09''E / 2450m, / 20– 23 / [in the label] 6 / [in the label] 2009 / H. S. Staude [in HSS]".

Description (based on Kenyan material): Wings. Male wingspan male 14 mm (forewing length 7 mm) (n=2); female 15–17 mm (forewing length 7–8 mm) (n=6). Females are larger and ground color is lighter. Wings straw brown, markings dark brown (males) or slightly darker brown than ground color (females). Forewing costa rust brown; antemedial and postmedial lines narrow, sharp, angled; postmedial line of forewing near costa slightly angled towards wing apex; medial line weak; terminal area dark brown; terminal line dark brown; fringes straw brown, unicolorous; lines continued on the hindwings. Discal spots dark, large in all wings. Wings colored below as above, slightly tinted with red, dark brown markings missing, discal spots weaker. Markings similar in females, except lines more diffuse, terminal area not dark brown as in male. Head. Labial palpi short, upturned, light brown. Proboscis short. Frons and vertex rust brown, smooth scaled; collar rust brown. Dorsal surface of the antennae rust brown at base, lighter towards apex. Male antennae bipectinate; female antennae fasciculate. Thorax. Concolorous with wings; legs concolorous with wings, partially rust brown; foreleg tibial spurs absent; midleg tibia with two terminal spurs, of unequal length; male hindleg tibia slightly enlarged, without hair pencils and spurs; tarsomeres of male hindleg tarsus fused, pretarsus absent; female hindleg tibia with two terminal spurs. Abdomen. Concolorous with thorax and wings. Tympanal organs large, round almost joined medially; ansa wide at base, expanding, narrowest below hammer-headed apex. Sternites 3–7 of male weakly sclerotized, unmodified; anterior margin of male sternite 8 medially concave; base rather well developed (high); mappa bare, round; cerata present, symmetrical, slightly curved, apical brushes absent; tergites 2–8 of male weakly sclerotized, unmodified. Female sclerites undifferentiated. Male genitalia. Small, fused, roundish. Uncus absent; socii present as a group of setae only; dorsal lobe of valva (valvula) soft, setose, long; ventral lobe of valva (sacculus) rudimentary, upturned medially, sacculus margin covered with short setae, short coremata laterally; juxta weakly sclerotized, with narrow wing-like processes; vinculum wide, u-shaped. Aedeagus rather thick, bent ventrally less than 90 degrees; caecum long, round; distinct, keel-shaped extension in ventral part; vesica unsclerotized. Female genitalia. Papillae anales soft, setose; apophyses posteriores slightly longer than apophyses anteriores; region around ostium bursae weakly sclerotized; proximal part of ductus bursae narrow, then wider, ball-shaped; ductus seminalis membranous, opens from ductus bursae laterally; corpus bursae elongated; partially weakly spinose.

Etymology. The name arabukoensis is derived from the type locality, Arabuko Sokoke National Park, Kenya.

Biology and distribution. I. arabukoensis is known from the type locality in southeast Kenya, ( Fig. 43 ); the Honde Valley, Zimbabwe; and the Nyungwe Forest Reserve, Rwanda ( Fig. 41 ). This species may be associated with (wet) forest or marsh mosaic habitats. The three known populations of this species are isolated from each other. The Arabuko Sokoke National Park in Kenya is under threat of slash and burn practises, thus placing the population in a vulnerable position. The immature stages are unknown.

Remarks. Three specimens from the eastern highlands of Zimbabwe, and three specimens from Nyungwe Forest Reserve, Rwanda are larger and colored differently from the straw brown Kenyan material ( Figs. 31, 34 ), although the maculation is generally similar. The forewing apex of Zimbabwe specimens is yellowish, the transverse posterior line is distinct, rather smooth, and the discal spots are rather weak ( Fig. 32 ); the Rwanda specimens are greenish ( Figs. 33, 35 ). There are small differences between these various populations in the curvature of the male aedeagus and shape of the keel-shaped appendix of the aedeagus, but otherwise the male and female genitalia, including the male 8th sternite, are generally similar ( Figs. 36–40 ). The male genitalia capsule width, length and aedeagus length appear to correlate weakly with forewing length (not tested statistically due to small number of specimens), appearing approximately the same in all specimens ( Fig. 42 ). The status of the Zimbabwe, Rwanda and Kenya populations remains to be investigated in greater detail; DNA analysis is highly desirable.

Figures

FIGURE 41. Map of Africa and Madagascar displaying the known distribution of Isoplenodia species.

FIGURE 42. Correlation between male forewing length and three male genitalic characters in Isoplenodia arabukoensis. Genitalic height = maximum distance between tegumen and saccus margins; genitalic width = maximum distance between genitalic capsule margins; aedeagus length = maximum distance from the apex to the caecum. Based on specimens from Kenya (PS 1329), Zimbabwe (PS 1392, PS 1393) and Rwanda (PS 1495).

FIGURE 43. Type locality habitat of Isoplenodia arabukoensis: southeastern Kenya, Arabuko Sokoke National Park. Photo H. S. Staude.

FIGURES 2 – 8. Adults of Isoplenodia spp. Diagnostic features indicated. 2. I. arrogans Prout male, Madagascar, early October 1934 (BMNH). 3. I. arrogans Prout female (syntype), Madagascar, February – April (BMNH). Photo courtesy of the Natural History Museum, London, UK. 4. I. vidalensis male (holotype), South Africa, 13 November 1999 (TMP). 5. I. vidalensis female (paratype), South Africa, 13 November 1999 (HSS). 6. I. kisubiensis male (holotype), Uganda, 25 November 2005 (TMP). 7. I. arabukoensis male (holotype), Kenya, 21 July 2002 (TMP). 8. I. arabukoensis female (paratype), 21 July 2002 (HSS). Scale bar = 10 mm.

FIGURES 15 – 20. Male genitalia of Isoplenodia spp. Diagnostic features indicated. 15. I. kisubiensis (holotype), genitalia. Prep. No. 1326 / Pasi Sihvonen (TMP). 16. I. kisubiensis (holotype), 8 th sternite. Prep. No. 1326 / Pasi Sihvonen (TMP). 17. I. kisubiensis (holotype), aedeagus. Prep. No. 1326 / Pasi Sihvonen (TMP). 18. I. arabukoensis (holotype), genitalia. Prep. No. 1329 / Pasi Sihvonen (TMP). 19. I. arabukoensis (holotype), 8 th sternite. Prep. No. 1329 / Pasi Sihvonen (TMP). 20. I. arabukoensis (holotype), aedeagus. Prep. No. 1329 / Pasi Sihvonen (TMP).

FIGURES 21 – 29. Female genitalia of Isoplenodia spp. Diagnostic features indicated. 21. I. arrogans Prout (syntype), genitalia. Geometridae genitalia slide No. 22584 (BMNH). Photo courtesy of the Natural History Museum, London, UK. 22. I. arrogans Prout (syntype), ostium bursae. Geometridae genitalia slide No. 22584 (BMNH). Photo courtesy of the Natural History Museum, London, UK. 23. I. arrogans Prout (syntype), corpus bursae. Geometridae genitalia slide No. 22584 (BMNH). Photo courtesy of the Natural History Museum, London, UK. 24. I. vidalensis (paratype), genitalia. Prep. No. 1232 / Pasi Sihvonen (HSS). 25. I. vidalensis (paratype), ostium bursae. Prep. No. 1232 / Pasi Sihvonen (HSS). 26. I. vidalensis (paratype), corpus bursae. Prep. No. 1232 / Pasi Sihvonen (HSS). 27. I. arabukoensis (paratype), genitalia. Prep. No. 1327 / Pasi Sihvonen (HSS). 28. I. arabukoensis (paratype), ostium bursae. Prep. No. 1327 / Pasi Sihvonen (HSS). 29. I. arabukoensis (paratype), corpus bursae. Prep. No. 1327 / Pasi Sihvonen (HSS).

FIGURES 31 – 35. External variation in I. arabukoensis. 31. Male (holotype), Kenya, Gedi, Arabuko Sokoke Forest Reserve, 21 July 2002 (TMP). 32. Male, Zimbabwe, Honde Valley, Aberfoyle, 18 October 1990 (TMP). 33. Male, Rwanda, Nyungwe Forest Reserve, 20 – 23 June 2009 (HSS). 34. Female (paratype), Kenya, Gedi, Arabuko Sokoke Forest Reserve, 21 July 2002 (HSS). 35. Female, Rwanda, Nyungwe Forest Reserve, 20 – 23 June 2009 (HSS). The genitalia of these specimens are illustrated in Figs. 36 – 40. See text for elaboration.

FIGURES 36 – 37. Female genitalia of I. arabukoensis. 36. Female (paratype), Kenya, Gedi, Arabuko Sokoke Forest Reserve, 21 July 2002. Prep. 1327 / Pasi Sihvonen (HSS). 37. Female, Rwanda, Nyungwe Forest Reserve, 20 – 23 June 2009. Prep. 1496 / Pasi Sihvonen (HSS). The adults of these specimens are illustrated in Figs. 34, 35.

FIGURES 38 – 40. Male genitalia of I. arabukoensis. 38. Male (holotype), Kenya, Gedi, Arabuko Sokoke Forest Reserve, 21 July 2002. Prep. No. 1329 / Pasi Sihvonen (TMP). 39. Male, Zimbabwe, Honde Valley, Aberfoyle, 18 October 1990. Prep. No. 1393 / Pasi Sihvonen (TMP); genitalic capsule is angled. 40. Male, Rwanda, Nyungwe Forest Reserve, 20 – 23 June 2009. Prep. 1495 / Pasi Sihvonen (HSS). The adults of these specimens are illustrated in Figs. 31 – 33.