ARACHNIDA > OPILIONES > Phalangiidae > Leiobuninae

Leiobunum blackwalli is a long-legged harvestman with a mid-sized body of around 5mm. The species is sexually dimorphic in terms of both size and appearance. By comparison with the males, the females have a somewhat elongated body, described as being pale silvery-brown with a dark truncated saddle that widens towards the rear giving it a somewhat triangular shape. Males are smaller and rounder, and uniformly orange-brown. The ocularium is smooth and there is no trident.

They are superficially similar to the more frequently encountered Leiobunum rotundum, particularly the males as they don't have any definable markings. Fortunately, there is a specific and very easy to see distinguishing difference between these two species, and that is that Leiobunum blackwalli has pale eye rings separated by a narrow dark mid-line, whereas Leiobunum rotundum has dark eye rings separated by a pale mid-line.

Another important feature is that the trochanters are dark, albeit with some pale areas, which helps separate them from another not dissimilar long-legged species Opilio canestrinii, which has orange trochanters contrasting with dark legs.

Leiobunum blackwalli is a relatively common and widespread harvestman across much of central and southern Britain, but becoming far less frequent further north. It is predominantly a deciduous woodland species where it will most likely be found on raised vegetation. Adults start appearing in June, peaking around September and persisting through to the following year. Juveniles hatch in the spring initially staying at ground level, but then moving on to and up the different layers of vegetation as they grow.

To date, I've only photographed three individuals, all of which were females.