Species of the Month: September 2025

Opilio canestrinii

One of around 34 species of Harvestman (Opiliones) found in the UK, Opilio canestrinii is a fairly recent arrival which has expanded quickly since the first UK sighting in 1999. The species favours urban habitats, and is frequently found on walls and buildings, making it easy to spot and record. 

A relatively large species in total circumference, the body is 6-8mm with very long dark legs. There is generally orange colouration on the grey body, with a paler band running along the back, often with alternating pale and dark lines running across the body. There may be some confusion with the Leiobunum species (also orangey with dark legs), however the pale joints between the body and legs (trochanters) contrasting with the dark legs are diagnostic. 

If you are unsure about identifying this species, you may like to use ObsIdentify, a photo identification app which is usually accurate with this species. You can also email photos to info@sewbrec.org.uk or post in our Facebook group for help with identification.

Opilio canestrinii is now widespread throughout the SEWBReC area, though there are only 474 records in Wales (372 in SEWBReC area); view a 1km distribution map here.

You can find more image and information about Opilio canestrinii from the Spider and Harvestman Recording Scheme, Field Studies Council Harvestman Identikit (key here) and NatureSpot. You can view Wales-wide distribution map here.