There is sexual dimorphism with the males having a shorter and generally plainer-coloured orangey body and the females a longer, darker body.
The legs are very long and often very dark - almost black - in sharp contrast to light trochanters. In females, the trochanters can appear orange and the legs black. Another noticeable field character in some females, including juveniles, are fine lateral stripes, broken down a broad middle section, each of which consists of one dark and one light contrasting stripe.
Some individuals have a noticeable pale eye-ring, especially juveniles.
Because the legs are very long there is potential for confusion with Leiobunum species, but a key difference is the colour of the trochanters which have dark and light patches in Leiobunum rather than the all-pale trochanters of Opilio canestrinii contrasting with dark femurs.
A recent immigrant to the UK that has become a very common species over a very short period of time. In Hillyard (2005) it is barely mentioned, presumably because it was a recent arrival. The fist record in the British Arachnological Society's Spider and Harvestman Recording Scheme is from 1999. It is now found widely, and increasingly frequently, over much of the UK. For the most up-to-date distribution map, visit the relevant page of the Spider and Harvestman Recording Scheme . Wijnhoven (2009) states that it was originally known from Italy and has spread over the rest of Europe in the last couple of decades.
Markedly synanthropic and often found on walls and tree trunks as well as the field and shrub layers of vegetation. It also occurs away from urban areas in more natural habitats.
Adults occur in greatest numbers during the late summer and autumn (peak in August and September), but it can be found well into the early part of winter.
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 Unpublished.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.