Iconic specimens in the Iziko entomology collection: Mbashe River Buff


The Mbashe River Buff, Deloneura immaculata Trimen, 1868 (Lycaenidae) was collected along the Mbashe River near Fort Bowker in the Eastern Cape towards the end of December 1863 by Colonel James Henry Bowker and described by Roland Trimen five years later (Trimen 1868).

The species is only known from three specimens, two of which (a female and male) are in the entomology collection of the Iziko South African Museum in Cape Town. The third male specimen was originally in Roland Trimen’s personal collection, which eventually was bequethed to the Natural History Museum in London. Despite numerous efforts over the last century to rediscover the species, no further specimens have ever been seen again. The species is regarded as Extinct under the IUCN criteria for red listed threatened species (Henning et al. 2009; Mecenero et al. 2013).

Note from Trimen’s original description: ”I regret that paucity of examples of the species on which this genus is founded (of the three individuals before me two are the property of the South-African Museum) prevents me from actually ascertaining by dissection whether the fore tarsi are identical in both sexes; but, judging from the external characters of the abdomen, the much larger size, and the more rounded wings of one specimen, I believe it to be a female, while the other two have the aspect of males. The fore tarsi are precisely similar in these three specimens.”

Notes on behaviour from Trimen’s original description: “Entomology is indebted to Mr. J. H. Bowker for the discovery of this remarkable butterfly, which took place at the end of December, 1863. In some letters addressed to me about that time, Mr. Bowker notes the species as “a true forest insect, only found in or at the edge of woods, and appearing but for a few days. In flight they resemble Acraea horta, and still more the yellow treemoth [=Euproctis], whirling slowly, with flapping wings, round the tops of trees, rising and falling, sailing away and returning.”

There is a possibility that the species will be re-discovered. The cryptic habits of the adults, and remote and relatively inaccessible nature of the type locality, has hindered comprehensive exploration in search of extant populations. Caterpillars of other species in the genus Deloneura (of which there are seven species in total, all of which are endemic to the Afrotropical region) feed on lichen on tree trunks in association with ants. The adult butterflies spend much of their time perched very still and well camouflaged on tree branches, only taking flight if disturbed.

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