The
Xyelidae are a small family of
sawflies known from fewer than 50
extant species in five genera, but with an extensive
fossil record; they are the oldest fossil
Hymenoptera, dating back to the
Triassic, between 245 and 208 million years ago. Most species occur in the Northern Hemisphere, especially in
boreal regions, though there are a few
neotropical species. Most are associated with
conifers (esp.
Pinus and
Abies), where the
larvae feed on
pollen or within buds, though larvae of a few species feed on the leaves of
deciduous trees.