Bicyclus ignobilis Butler

Brattström, Oskar, Aduse-Poku, Kwaku, Collins, Steve C. & Brakefield, Paul M., 2015, Revision of the Bicyclus ignobilis species-group (Lepidoptera: Nymphalidae: Satyrinae) with descriptions of two new species, Zootaxa 4018 (1), pp. 57-79 : 64

Bicyclus ignobilis Butler stat. rev.

( Figs. 2–6 , 27–28 , 32–33 )

Mycalesis ignobilis Butler 1870 ( Gold Coast = Ghana)

Bicyclus ignobilis eurini Condamin & Fox 1963 (Lolodorf, Cameroon) syn. nov. Bicyclus ignobilis acutus Condamin 1965b (Bwamba Forest, Uganda) syn. nov.

Material examined. Type material: Holotype ( ignobilis ) ♀: Gold Coast ( Ghana), No further data, BMNH (E) #1054538 ( BMNH). Holotype (acutus) ♂: Uganda, Buamba Forest (0°49’N, 30°04’E), Sem[u]liki Valley, 2,300– 2,800 ft., 3–7.xi.1911, S.A. Neave leg., No. Rh. 18232 ( BMNH). Allotype (acutus) ♀: Uganda, Budongo Forest (1°45’N, 31°25’E), Unyoro, 3,400 ft., 11–15.xii.1911, S.A. Neave leg., No. Rh. 18233 ( BMNH).

Non-type material. 276 ♂ & 453 ♀. See Supplementary Table 1.

Diagnosis. Both sexes of B. ignobilis usually lack an eyespot in space 3 on the ventral hindwing ( Figs. 2–4 , 32–33 ), while all other species in the ignobilis- group generally have this spot fully developed. However, there is variation in this trait and occasional specimens of B. ignobilis may have a fully developed eyespot. Nevertheless it is a useful initial diagnostic tool before looking at more subtle characters, but not something to alone rely on for identification. The male can be identified by the presence of an extended comb of short shiny black hairs extending from space 1c, in a direction towards the tornal point of the wing and partly covering a prominently enlarged section of vein 1b. The vein is enlarged for about one half to two-thirds of its total length starting from near the base of the wing, and the enlarged section is covered with modified beige scales clearly standing out from the darker colour of the wing ( Fig. 6 ). There are no traces of androconial structures on the dorsal forewing. The female is harder to identify in cases where the eyespot in space 3 on the ventral hindwing is not missing, but in general the shape of the forewing apical band should be sufficient. Specimens from the eastern part of the range ( Fig. 33 ) have vein 4 more heavily marked in dark, almost breaking up the apical patch in a similar way as in B. maesseni ( Fig. 31 ) (see section on female identification below). However, the species are only co-occurring in West Africa, where B. ignobilis generally have a more solid apical patch ( Fig. 32 ). It is therefore a quite reliable identification cue in the areas where the two species occur sympatrically. Across its entire range there is a clinal change in the wing pattern in both sexes of B. ignobilis . The main difference is a gradual change in the shape of the ventral hindwing discal band that gets a sharper angle at the distal end of the cell of both wings in an eastwards direction. Another less marked difference is a generally cleaner white and better-developed apical band in males from further east, western males tend to have faintly marked yellow white patch ( Fig. 3 ). In addition, as stated above, the female band is often a little more broken up by vein 4 in the eastern parts of the range.

Supression of subspecific taxa. The rather strong geographic variation in the species was the basis for the descriptions of two additional subspecies. Specimens from between Liberia and western Nigeria were assigned to the nominate subspecies (Type locality: Ghana), while the name B. ignobilis eurini Condamin & Fox 1963 was assigned to specimens between eastern Nigeria and DRC (Type locality: Lolodorf, Cameroon). The populations found in the extreme east of the range, mainly Uganda and Tanzania, were assigned the name B. ignobilis acutus Condamin 1965b (Type locality: Bwamba Forest, Uganda). However, Condamin (1973) later suggested that this difference might indeed be clinal, and it is likely that he saw more material of an intermediate morphology in the time between describing the subspecies in the first place up until writing his 1973 monograph. After investigating over 700 specimens from across the entire range of the species, without finding any area where a sharp transition between the previously described subspecies takes place, we hereby suppress eurini and acutus as valid names and consider B. ignobilis as a single taxon with a marked clinal variation.

Distribution. The species is distributed between Sierra Leone and Central Uganda, reaching the Lake Victoria forests in Eastern Tanzania. It extends further south than any other species in the ignobilis -group with a small number of records in southern DRC ( Fig. 27–28 ).

Comments. The original description of the species ( Butler 1870) does not mention anything regarding the male morphology, and it is likely that the single female individual in BMNH currently recognised as a type (Voucher ID: BMNH(E)1054533) was the only specimen available to Butler. Aurivillius appears to have made the first published description of B. ignobilis males. In his report ( Aurivillius 1893) on material collected by Yngve Sjöstedt in Cameroon between 1890 and 1891, he clearly notes the black haircomb on the hindwing. Sjöstedt was reported to have collected two pairs of the species, and four matching specimens bearing labels with his name are still in the collections of NHRS. The types of Bicyclus ignobilis eurini were not studied (they are located in the Carnegie Museum in Pittsburgh, USA). However, the original publication ( Condamin & Fox 1963) has detailed photos of the holotype and allotype, and describes the main morphological characters in extensive detail. We did investigate several specimens from the same general location in Cameroon (Supplementary table 1).

Figures

FIGURES 2 – 6. Bicyclus ignobilis (Butler 1870). 2. Male, DRC (OB-VIE- 0046) 3. Dorsal forewing and ventral hindwing showing the main morphological differences in the western populations. The shown specimen (OB-IND – 0046) is from eastern Nigeria. A female from the western region is shown in Fig. 32. 4. Female, DRC (OB – VIE – 0047). 5. Male genitalia, Uganda (OB – ABRI – 0092). 6. Androconial structures (OB – ABRI – 0092). There is a comb of black hairs (encircled in white) covering an enlarged section of vein 1 b on the dorsal hindwing. The cell-brush is clearly visible in the image and there are no forewing androconial structures.

FIGURES 27 – 29. Distribution maps for the Bicyclus ignobilis species-group. Records of different species from the same site have been slightly offset when presented in the same map so that all species symbols can be clearly seen. Multiple records close to each other have been collapsed to a single point. The complete distributional data is available in Supplementary Table 1. 27 – 28. B. ignobilis (Open Squares) and B. maesseni (Open Crosses). 27. West Africa up to the Cameroonian border. 28. Cameroonian border and eastwards. 29. Remaining species occurring between Nigeria and Eastern DRC: B. brakefieldi (Filled Circles). B. ottossoni (Filled Crosses). B. rileyi (Open Circles). B. vandeweghei (Filled Diamonds).

FIGURES 30 – 36. Identification of females from the ignobilis- group. The images are not shown to scale, arrows indicate the main characters of importance for identification. 30. B. rileyi is much larger than any other species and the light markings in the apical patch continue below the eyespot in space 2, and often reach the lower margin of the wing. 31. B. maesseni has the edge of the apical patch more broken up in the area closest to the apical eyespot. Also, vein 4 is heavily marked with darker scales, breaking up the patch along its entire length. 32. B. ignobilis (western part of range) almost always lack the ventral hindwing spot in space 3, the apical patch is also much more solid than in B. maesseni with vein 4 just making a dark indentation in the basal part of the light patch. 33. B. ignobilis (eastern part of range) has vein 4 more heavily darkened so that the apical patch is sometimes fully broken up in sections. This makes them appear similar to B. maesseni, but the latter species is not sympatric in the eastern part of the range of B. ignobilis. The ventral discal band gradually gets a more pronounced edge at the end of the cell on both wings in a clinal fashion towards the east of the species range. 34. In B. ottossoni the basal part of the apical patch lacks indentations of dark scales along vein 4. The outer borders of the patch are much better defined than in the other species. The distal margin of the forewing is also much less convex, giving the wing a more squared shape. 35. B. vandeweghei have much more prominent light shading around the hindwing eyespots. The apical patch is otherwise similar to B. ignobilis. 36. B. brakefieldi have a more yellowish colour in the apical patch, and the part of the patch being placed basally of the eyespot is a bit fainter than in other species.