Xyelidae

The Xyelidae are a comparatively species-poor family of sawflies, comprising about 80 extant species in five genera worldwide, and is the only family in the superfamily Xyeloidea. The fossil record of the family is extensive, comprising more than 120 species and including the oldest fossil Hymenoptera species dating back to the Triassic, between 245 and 208 million years ago. Xyelidae are sister to all other contemporary lineages of Hymenoptera and have many ancestral morphological features. The extant species occur in the Northern Hemisphere, especially in boreal regions of the Holarctic, though there are a few Oriental species. Two genera and about 15 species occur in Europe. Considering additional fossil records from Australia, South Africa and Argentina, the extant species display a relict distribution. The species in the subfamily Xyelinae are associated with conifers (esp. Pinus and Abies), where the larvae feed on pollen or within buds. The larvae of the subfamily Macroxyelinae feed on the leaves of deciduous trees (various Juglandaceae and Ulmus). The family is characterized by the appendages of the head, which are remarkable in that the antennae and palpi are nearly leg-like in structure, with a long basal segment followed by a series of tiny segments, as in the tibia-tarsus.