Strongylogaster mixta - Belted Fern-sawfly

Widespread but local throughout much of Britain (Musgrove, 2023).

The abdomen usually has tergites 2 to 5 banded reddish-yellow. The clypeus and labrum are black as are all the femora except at the extreme apex. The mesopleura are shiny and scarcely punctured.

Strongylogaster mixta larvae feed on Lady Fern, Bracken, Male Fern and possibly other ferns. The ova are deposited into fronds before they unfurl. The ova are loose and begin hatching after about 5 days. Late instar larvae are recognisable by the greenish grey ground colour on the upper surface, a mostly dark brown or black head and the presence of a black spot on the supra-anal lobe. Larvae cocoon overwinter in the pith of stems (blackberry, etc.).

Jump to other Strongylogaster species

Size: 7 - 9mm

GB IUCN Status: Least Concern
GB Rarity Status: None

Distribution: England, Scotland, Wales, Ireland

Flight period: April to June

Plant associations: Athyrium filix-femina (lady fern), Dryopteris species incl. Dryopteris wallichianna (Alpine Wood Fern), Dryopteris filix-mas (Male Fern) and Pteridium aquilinum (Bracken). 


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.

Musgrove, A.J. 2023. A review of the status of sawflies of Great Britain - Phase 2: The Athaliidae and the Tenthredinidae (excluding Nematinae). Natural England, unpublished

Macek, J., 2010. Taxonomy, distribution and biology of selected European Dinax, Strongylogaster and Taxonus species (Hymenoptera: Symphyta). Acta Entomologica Musei Natioalis Pragae, 50(1).