Tree Fern Bembidion Ground Beetle (Bembidion dicksoniae)  

The twelve species of the genus Bembidion, known to occur on Saint Helena, prey on endemic weevil species (Curculionidae), which often are dependent on rotten wood.  

In recent times, however, the climatical conditions in the remaining endemic cloud forests of Saint Helena have changed – less rain led to a much more open canopy, which again led to much drier conditions at ground level, which again seems to be quite detrimetal to the rotting process, leading to a lack of rotten wood.  

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The Tree Fern Bembidion Ground Beetle was found mostly inside, but sometimes also on the surface of the stems of the Saint Helena Tree Fern (Dicksonia arborescens L’Hér.).  

See also Thomas Vernon Wollaston in the year 1877 (Coleoptera Sanctae-Helenae).:  

“The modus vivendi of this Bembidium is precisely similar to that of the preceding and four following ones, – it having been obtained from the interior of the damp fibrous stems of the dead tree ferns on the high central ridge in the vicinity of Diana’s Peak. It is without doubt extremely rare; nevertheless I met with 17 examples of it, from first to last, by bringing amay portions of the old Dicksonias and breaking them up carefully, at home, into small fragments, over a white cloth, – which embodies a far more successful method for securing these Filicophilous Coleoptera than by examining the trunks hastily in situ.”  

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The most recent searches (2005 to 2006) failed to find any sign of the Tree Fern Bembidion Ground Beetle (and the other endemic Bembidion species), the species is therefore considered very likely extinct.  

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References:  

[1] T. V. Wollaston: Coleoptera Sanctae-Helenae. London: John Van Voorst, Paternoster Row 1877 
[2] H. Mendel; P. Ashmole; M. Ashmole: Invertebrates of the Central Peaks and Peak Dale, St Helena. 2008 

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edited: 30.05.2021