Phalangium diadema Megabunus diadema is a species of harvestman distributed in Western Europe, where it has been found in Iceland, Faroe Islands, Western Norway, Great Britain, Western France, Belgium and Northern Spain.

[1] It is commonly found among moss and lichens, and has a cryptic coloration that blends with this habitat, rendering it almost invisible when it is not moving.

[3] Its prominent pair of eyes is equipped with a spiny "crown".

[4] The gregarines Actinocephalus megabuni and Doliospora repelini (Eugregarinorida), and the mite Leptus beroni were found to parasitize on this species.

[5] During a study of woodland in Scotland, they were found to be most active during March, June to July and December; in montane regions of Wales they only occurred in August, while they were found all year round in English woodland, with a peak from May to August.