1 (furca) The springing organ of Collembola, which arises from the fourth or fifth abdominal segment. The furcula comprises a single basal portion, the manubrium, which gives rise to two dens, which terminate in lamellate mucrones (see mucro). It is bent forwards and beneath the body to engage on a ventral tube or retinaculum, which acts as a catch. When the furcula is released, the energy stored propels the animal upwards and forwards, sometimes in a tumbling fashion.
2 The wishbone of birds and some Therapoda, supposedly formed by the fusion of clavicles and interclavicle.