Its a Sawfly, But Not Really

Tenthredo livida is a common sawfly of holartic distribution that is often found in hedgerows and woodlands. The female lays eggs into plant tissue, using saw-like ovipositor to make the inscision. Larvae are polyphagus, feeding on a variety of plats such as hazel, willow and even bracken. The adults will hunt flies and take nectar from plants (1).

Tenthredo livida

Interestingly, calling T. livida a sawfly, or "Symphyta", is now considered incorrect. The Symphyta are a basal grade that leads to the long waisted hymenoptera. Therefore Symphyta is not a monophyletic group, that is within the group not all relatives are included (2). The terms "Symphyta" and saw fly are still used however, in an informal way.
References:

1. Calmasur and Ozbek, 2006. Proceedings of the Entomological Society of Washington 108 pp. 139-144
2. Resh and Carde, 2009. Encyclopedia of Insects p. 474