Xyelidae
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The Xyelidae is a small family of sawflies known from fewer than 50 extant species in 5 genera, but with an extensive fossil record; they are the oldest fossil Hymenoptera, dating back to the Triassic, some 200 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.
The family is characterized by the appendages of the head, which are truly 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. It is tempting to speculate that there is a homeobox-gene explanation for this unusual anatomy, as mutations of this gene region in other insects can cause the mouthparts and antennae to become leg-like.
[edit] Extant Genera
- Macroxyela Kirby, 1882
- Megaxyela Ashmead, 1898
- Pleroneura Konow, 1897
- Xyela Dalman, 1819
- Xyelecia Ross, 1932
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