Megabunus diadema is an unmistakable harvestman which is, nonetheless, easily overlooked! This is because of its very small size (easily mistaken for a juvenile of another species) and cryptic colouration. The brown and black markings over a silvery background and double-waisted saddle are very beautiful but also afford good camouflage, e.g. on lichens. When seen up close though it is the unmistakable ocularium which catches they eye, being adorned with five pairs of extremely long tubercles. There are also long spines on the distal ends of the leg segments and around the margin of the cephalothorax.
Megabunus diadema is widespread over the UK and most common in the wetter upland areas - see the distribution map of the Spider and Harvestman Recording Scheme . In Europe it is not so widespread, being mostly confined to northern latitudes and the Pyrenees. Males are hardly ever seen and parthenogenetic reproduction has been shown to occur.
Megabunus diadema is strongly more humid environments especially woodlands, heathlands and moorland and is found it greatest abundance in the upland and western areas (i.e. the wetter areas of the UK). It occurs in and above the ground layer. In moorland areas, it may frequently be found on the bare face of rocks (where it can be well camouflaged). I frequently find it associated with weeds growing at the margin between the outside walls of my house and the surrounding block paving (in a town on the edge of the West Pennine Moors).
Although adults can, apparently, be found at any time of year, there seems to be a distinct peak around late spring/early summer.
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 Unpublished.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.