Charaxes Epijasius

''Charaxes epijasius'', the cream-bordered charaxes or Sahel charaxes, is a butterfly in the family Nymphalidae. It flies through most of the Savannah of the Afrotropical realm except southern Africa.

Description

''Charaxes epijasius'' is a medium to large butterfly. West African and Ethiopian examples tend to be smaller than more central and eastern African specimens. The male has a wingspan of 62–84 mm in West Africa, up to 80-95mm further east, females larger up to 95-102mm. Each hindwing bears two tails, characteristic of most species of the genus, which tend to curve slightly towards each other to a variable degree. The upperside ground colour of the wings is very dark brownish-black, with a slight purplish bloom. Forewing sometimes with suggestion of slightly lighter discal bars, usually with no post-discal spots on the forewing, though sometimes one or two near the costa, often faint; hindwing with pale whitish-yellow patch near costal border, dusted with blackish scales; admarginal outer band of both wings light golden-yellow colour, divided by black-scaled veins. Hindwing has a post-discal broad wedge of bright sky blue clearly demarcated from the admarginal yellow by a well-defined black scalloped border. The underside has a characteristic mosaic appearance, in common with other members of the ''Charaxes jasius'' species Group, traversed by a jumble of bands and of brown, reddish, and grey-blackish patches, all edged with a filigree of white. Beyond the inner mosaic, a white complete discal band bridges across fore- to hindwings, tapering down towards the forewing costa. The outer orange marginal coloration is present on the underside also, whitish stripes are evident within the marginal border, above each greyish vein. The female resembles the male but is larger.

Type

The type location is Senegal.

Hybridisation

Where ''C. saturnus'' is sympatric with ''Charaxes epijasius'' tat.rev.2005/small>, over an extensive zone of overlap, the two species hybridize regularly, producing highly variable transitional specimens (''C. saturnus'' x ''C. epijasius''). The distribution range of hybrid forms extends from Ethiopia to Western Kenya & Northern Tanzania. The variable hybrid forms have historically been named as ''harrisoni'', ''saturnalis'', pl. 4, f. 20-24, pl. 5, f. 25-28; TL= "Kenya, South Kavirondo, Suna" and ''pagenstecheri''Poulton, E.B. (1926). Mimicry in African Butterflies of the genus Charaxes, with a classification of the species. III. Internationaler Entomologen-Kongreß, Zürich, Juli 1925, Band II. pp531-532,57
accessible pp531-532,570
/ref>. Observation of hybrid forms in Tanzania, as an example, beyond the recognised range of ''C. epijasius'', strongly indicates that the hybrid forms may exist as fertile hybrids, at a lower prevalence than the relatively more stable phenotype of ''C. saturnus''. More detailed phylogenetic research and breeding studies are required to elucidate further the relationships between the two species and their intermediate hybrid phenotypes, and the degree of fertility exhibited amongst their highly variable hybrid forms.

Subspecies

*''C. epijasius epijasius'' has a consistent unmistakeable appearance across its distribution. Wingspan is regionally variable to a degree. No subspecies are known.

The ''Charaxini'' taxa ''harrisoni'', ''saturnalis'', and ''pagenstecheri'' are now thought to be at least partially fertile hybrid variable phenotypes of ('' C. saturnus'' x ''C. epijasius''). This suggests that evolutionary divergence to fully stable species separation between ''C. epijasius'' and ''C. saturnus'' is not complete.

Related species

Historical attempts to assemble a cluster of presumably related species into a "''Charaxes jasius'' Group" have not been wholly convincing. More recent taxonomic revision, corroborated by phylogenetic research, allow a more rational grouping congruent with cladistic relationships. Within a well-populated clade of 27 related species sharing a common ancestor approximately 16 mya during the Miocene, 26 are now considered together as The ''jasius'' Group. One of the two lineages forms a robust clade of seven species sharing a common ancestor approximately 2-3 mya, i.e. during the Pliocene

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