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HYMENOPTERA, Xyeloidea - Xyelidae

The small sawflies are less than 11 mm. long. They differ from other sawflies in having three marginal wing cells and the third antennal segment being very long. The larvae feed on the wood and pinecones of various trees, but the damage that they cause is slight compared to other members of the Symphyta.

This family of sawflies contains fewer than 53 described 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 distinct 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 may cause the mouthparts and antennae to assume structures that resemble legs.

There are not many species and none are of much economic importance.

References: <biology.ref.htm>, [Additional references may be found at: MELVYL Library ]