Oligolophus tridens has a dark, often abruptly truncated, saddle that is more or less rectilinear, although it can also have a narrow waist. But in some specimens, the colour of the saddle and the rest of the body is similar making the saddle hard to see; such specimens have a very drab, overall darkish appearance. A hand lens will reveal a trident which, although comprised of quite long members (e.g. in comparison to Paroligolophus agrestis), can be quite inconspicuous. This is especially the case when viewed from above, because the members are normally upward pointing, slender and the same colour as the rest of the body. The trident members are of equal length or with the middle member slightly longer and more forward pointing in the female.
Many sources note that some specimens of Oligolophus tridens are easily confused with Lacinius ephippiatus with which it shares many of the above features. However the trident members of Lacinius ephippiatus are slightly more slender and widely separated. A good view of the tubercles on the underside of the palpal femurs can also help - these are more or less just spines/hairs in Oligolophus tridens whilst they are definite spine-tipped tubercles in Lacinius ephippiatus. Similarly, the armament on the occularium is more or less just spines/hairs in Oligolophus tridens, but spine-tipped tubercles in Lacinius ephippiatus.
Although few sources mention it, separating Oligolophus tridens and Oligolophus hanseni can also be a challenge. The trident and associated tubercles are normally quite different. Although the trident members of both species are quite small, in Oligolophus hanseni they are normally conspicuously pale (even white) and, on very close inspection, tipped with black hairs. In Oligolophus tridens the trident tubercles can be pale, or the same colour as the body. Oligolophus tridens can have no additional tubercles to the side of the trident and as few as two behind, but in Oligolophus hanseni there are normally more than this to the side and behind. In Oligolophus tridens the two rows of tubercles on the ocularium are often neatly delineated in white, giving the impression of two white eye-rings. In Oligolophus hanseni there are white patches on the ocularium, but these don't usually give the impression of two neat eye-rings. When viewed from above, the rings of tubercles on the occularium appear to converge in the middle in Oligolophus tridens, but in Oligolophus hanseni they appear to converge more towards the front. Some specimens of Oligolophus hanseni have patches of white bordering the saddle, which don't occur in Oligolophus tridens.
Oligolophus tridens is extremely widespread over the whole of the UK- see the distribution map of the Spider and Harvestman Recording Scheme . It is also found all over Europe, only missing around the Mediterranean.
Oligolophus tridens is found in a wide range of habitats and micro-habitats. It can be found under stones and wood but also commonly in vegetation of virtually any kind. It may be especially common in the ground layer in woodland. It can frequently be swept from nettles, especially near water.
Adults occur from late summer to early winter with a very sharp peak numbers in September.
Hillyard, P. D., & Sankey, J. H. P. 2005. Synopses of the British Fauna (New Series) No. 4: Harvestmen. Third Edition.Field Studies Council, Shrewsbury.
Richards, P. 2010. Guide to Harvestmen of the British Isles. Field Studies Council, Shrewsbury.
Richards, P. 2017. Tabular key for Identification of British Harvestmen (Opiliones). Unpublished.
Wijnhoven, H. 2009. De Nederlandse hooiwagens (Opiliones). Nederlandse Entomologische Vereniging.