Missing legs

Last Saturday I was sent outside with yards of lights, wires and plugs with the instruction to light up the front of the house and the shrubs in the garden. Luckily it wasn't too cold and I didn't loose any finger to frost bite this year for a change! As I was fighting manfully with the topiary bush by the front door I found a late season Dicranopalpus ramosus on the wall.

It had a few legs missing, well in fact most of the legs are no longer there. This lack of limbs does not seem to have affected its survival this late into the season though. Like spiders there should be 4 pairs, but this is where the similarity between harvestmen and spiders stop. In harvestmen the second pair of legs are longer than the others and act as sensory limbs.

Harvestman belong to the order Opiliones, one of 11 orders placed in the class Arachnida. True spiders belong to the order Araneae. Harvestman differ from spiders by having only one pair of eyes on a centrally positioned ocularium, they do not have venom glands or hollow fangs with which to kill live prey and being devoid of silk glands do not spin webs. The cephalothorax and opisthosoma joined by a broad connection giving the whole body the appearance of being as one piece and the second pair of legs are longer than the other three pairs. 

Harvestmen will eat all kinds of food. Their omnivorous habits mean they will eat dead squashed slugs, bird droppings, jam, fruit and other plant remains, as well as live small invertebrates that they might catch. Generally they are nocturnal and can be found hiding under ivy, amongst grass stems, and other vegetation, under stones, bark and logs and inside cool damp buildings like sheds and outside toilets. Their common name derives from the fact that most are mature in autumn, at the time of harvesting.

The species name refers to the peculiar form of the palp in at least the first described species, D. gasteinensis (and D. ramosus), derived from di "two", cranium "head", and palpus. The size of the forked palms are clearly in the photos. Also characteristics of D. ramosus is the way on which it places it's legs when at rest.

D. ramosus is a southern species that has been slowly making its way north over the last few decades. It was first described from Morocco in 1909, and has moved northwards since then. In 1957 it was discovered and described in was first described in Bournemouth in 1957. Thouroughout the 1960s was only found on the south coast, but during the the 1970s and 1980s it spread over the south of England reaching as far north as Leicester by 1989. It reached south-east Ireland in 1994 and spread to north Wales and north-west England throughout the 1990s and into the 2000s.

The map below shows the recorded distribution throughout the UK (2).

References.

1: British Arachnological Society http://wiki.britishspiders.org.uk/index.php5?title=Category:Opiliones

2: Spider and Harvestman Recording Scheme. http://srs.britishspiders.org.uk/portal.php/p/Summary/r/view/s/Dicranopalpus%20ramosus