Abstract
We revise the Southeast Asian Pholcus bicornutus group in which males are characterized by a unique pair of horns on their ocular area, each of which carries at its tip a brush of hairs. In two species, the two hair brushes are ‘glued’ or ‘waxed’ together by an unidentified substance into a very consistently curved and pointed single median tip. In the other five species known, the hairs are unglued. We present a first revision of ocular modifications in Pholcidae and identify twenty supposedly independent origins. Most cases are in Pholcinae, and all but one case are limited to the male, suggesting sexual selection as the main driving force in the evolution of ocular modifications in Pholcidae. Previously, the Pholcus bicornutus group consisted of four species limited to the Philippines. We describe four new species, including three species from the Philippines (P. olangapo Huber, sp. nov.; P. kawit Huber, sp. nov.; P. baguio Huber, sp. nov.) and the first representative from outside the Philippines (P. mulu Huber, sp. nov. from Sarawak, NE Borneo) and provide new records and SEM data for three previously described species.
Highlights
When Eugène Simon returned from his expedition to Luzon in 1891, he brought with him, among others, a highly unusual pholcid spider species from caves near Manila
We revise the Southeast Asian Pholcus bicornutus group in which males are characterized by a unique pair of horns on their ocular area, each of which carries at its tip a brush of hairs
We present a first revision of ocular modifications in Pholcidae and identify twenty supposedly independent origins
Summary
When Eugène Simon returned from his expedition to Luzon in 1891, he brought with him, among others, a highly unusual pholcid spider species from caves near Manila. Struck by this feature, and devoted the only two figures in the original description of this new species Pholcus bicornutus Simon, 1892 to the male ocular region (Simon 1892: figs 3–4). The tips of these hair brushes were not separate as illustrated by Simon but appeared like ‘glued’ or ‘waxed’ together at their tips (Huber 2011a: figs 1566, 1568). Simon had clearly interpreted this as an artifact, and the latter author tended in the same direction, especially because in all specimens of two newly described close relatives of P. bicornutus (P. arayat Huber, 2011; P. pagbilao Huber, 2011) the hair brushes on the otherwise very similar ocular horns did not look like they were glued together. Sample sizes were small and no scanning electron images could be made of the two new species, so Huber (2011a) did not further dwell on the mysteriously joined hair brushes of P. bicornutus
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