Field characters

Prior to 2015, all UK Dicranopalpus records were considered to be D. ramosus, but a re-examination of some preserved specimens by Wijnhoven & Prieto (2015) found that some were D. caudatus (previously assumed to be a synonym of D. ramosus, but shown by them to be a valid separate species). So we now know that D. caudatus has occurred in the UK and may still do so. It is very similar to, and easily confused with, D. ramosus - both species have very distinctive 'forked' palps (due to a very elongated apophysis on the palpal patella) and at rest both species hold their legs straight out from its body in two narrow fans.

Wijnhoven & Prieto (2015) suggest that the two species may be told apart in the field, but more work on microscopically examined material is required to test the robustness of separating these species based on field characters. Therefore identifying the two Dicranopalpus species in the field should, for now, be done with caution.

For both species there is sexual dimorphism with males having a shorter body than the female. The females develop a protuberance at the end of the abdomen - a sort of large bump pointing backwards and more or less obliquely upwards. The tibial apophosis ('fork') on the palps of males is more slender than that of the female. In both sexes, Dicranopalpus caudatus is smaller than Dicranopalpus ramosus, but this kind of comparative character isn't that helpful in the field.

Male Dicranopalpus caudatus apparently never had a distinct dark patch across the cephalothorax - crossing the ocularium (which is often described as a Zorro mask in D. ramosus), although some darkening in this region can occur. Female Dicranopalpus caudatus are said to have a distinctly pot-bellied appearance when viewed from the side.

Distribution and ecology

Wijnhoven & Prieto (2015) confirmed two records of Dicranopalpus caudatus from southern England from a small amount of material they re-examined for their paper. One of these two records was dated 1957 (one of our earliest Dicranopalpus sp. records) and the other 1984. A number of harvestman recorders in the UK are currently examining preserved and new material to determine whether or not Dicranopalpus caudatus still occurs here and, if so, where.

Wijnhoven & Prieto (2015) have shown that over much of Europe, the ranges of D. caudatus and D. ramosus do not overlap (i.e. they are allopatric) with D. caudatus being largely confined to western, southern and eastern coastal areas of the Iberian Peninsula whilst D. ramosus if found on the northern coastal area of the Iberian Peninsula and over the rest of Northern Europe.

UK Dicranopalpus adults occur in greatest numbers during the late summer and autumn with peaks in August and September, but they are occasionally found in most months of the years, except those of early summer. We do not yet have sufficient information to be able to describe separate phenologies for D. caudatus and D. ramosus.

Bibliography

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.

Wijnhoven, H. and Prieto, C.E. 2015. Dicranopalpus caudatus Dresco, 1948: Not a synonym of Dicranopalpus Ramosus (Simon, 1909) but a valid species after all (Arachnida, Opiliones). Revista Iberica de Aracnologia, 26: 25-34