Harvestman  (Leiobunum rotundum)

Common and widespread (1).

This small arachnid has no separation between the head and the abdomen (4), giving the small, smooth body the appearance of an oval pin-head. The eight black legs are extremely long in relation to the body and can be self-amputated if the harvestman is in danger of predation (4). They will not regenerate (5). It has no fangs, no poison glands and no silk glands, but is not entirely defenceless as it possesses scent glands at the front of the body, to the sides of the two eyes (6) (7). These produce an unpleasant smelling secretion which is also distasteful to predators (7). The male is smaller but brighter in colour than the female, having a red-brown body, whereas the female has a brown body with a darker band along the top, and a black ring around each eye (1). The young look like small adults.

This harvestman is common and widespread all over Britain including the Channel Islands. It is also found in the Canary Islands and in Africa (1).

You can view distribution information for this species at the National Biodiversity Network Gateway.

Preferring damp habitats (3), the harvestman is often found resting on tree trunks (2) and among grass and leaf litter (8).

This harvestman is nocturnal and fairly active, walking raised up on its long legs (6) (9) (10). Indeed, the order name ‘Opiliones’ comes from the Latin word ‘opilio’ meaning ‘shepherd’, because walking harvestmen resembled the European shepherds who used to walk on stilts for an improved view of their flock. It is omnivorous, feeding commonly on small insects, plant material and fungi (6). The first pair of appendages (chelicera) near the mouth collects the food items and passes them to the second pair of appendages (pedipalps) where they are held and crushed by microscopic claws at the end of the pedipalps (4) (11). The food is chewed and ingested, rather than having the juices sucked out (7). The harvestman cannot live for long without water (4).

Harvestmen are most commonly seen in autumn, particularly during harvesting time (10) (11). They are often found on shady walls on the outside of buildings, where they cluster together in groups of up to 400 (12). They rest flat on the walls with their legs entwined, which serves several possible functions. By gathering together, the harvestmen may be creating an area of desirable temperature and humidity, or making use of the collective repellent power of their smelly defence (7). It has also been suggested that these aggregations pulsate in order to appear more intimidating to their predators (7).

Harvestmen mate by internal fertilisation, and females use their ovipositor to lay the already fertilised eggs into crevices in the soil (5). The eggs survive through the winter and hatch in spring (11).

This species is not threatened.

Conservation action has not been targeted at this widespread species.

There may be further information about this species available via the National Biodiversity Network Gateway.