The evolution of pedipalps and glandular hairs as predatory devices in harvestmen (Arachnida, Opiliones)

Pedipalps are the most versatile appendages of arachnids. They can be equipped with spines (Amblypygi), chelae (Scorpiones), or adhesive pads (Solifugae), all of which are modifications to grasp and handle fast-moving prey. Harvestmen (Opiliones) show a high diversity of pedipalpal morphologies. Some are obviously related to prey capture, like the enlargement and heavy spination of Laniatores pedipalps. Many Dyspnoi, by contrast, exhibit thin, thread-like pedipalps that are covered with complex glandular setae (clavate setae). These extrude viscoelastic glue that is used to immobilize prey items. Comparable setae (plumose setae) have previously been found in representatives of both Eupnoi a…