The Megalodontesidae are characterised by being broad bodied and flattened dorsoventrally, a character they share with Pamphiliidae. The hind margin of the pronotum is virtually straight. The antennae are 11 to 20 segmented with tongue or finger-shaped protrusions from the apices of each flagellal segment. The anal cell of the forewing is not contracted in the basal third and as a result it enclosed the scaly patch (that hooks onto the cenchri) present on the wing membrane that is normally outside the cell in other sawflies. The first abdominal tergite has a large central membranous patch reminiscent of the Cimbex species.
The larvae are gregarious and feed in silken webs on herbaceous plants. The adults are known for frequenting flowers.
The Megalodontesidae are known only from the Palearctic region. In Europe there are thought to be around 38 species. Three species of the genus Megalodontes are found in Northern Europe and have been mentioned historically as present in Britain. However, there are no specimens known to exist and Benson cast doubt as to whether any species actually existed in Britain.
Genus Megalodontes Latreille, 1802
Megalodontes cephalotes (Fabricius, 1781)
Benson, R. B. 1943: Some reputed British sawflies not found since Stephens's days (Hym., Symphyta). - The Entomologist's Monthly Magazine, Fourth Series, London 79(4): 5-7
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Liston A, Knight G, Sheppard D, Broad G, Livermore L (2014) Checklist of British and Irish Hymenoptera - Sawflies, ‘Symphyta’. Biodiversity Data Journal 2: e1168. https://doi.org/10.3897/BDJ.2.e1168