Strongylogaster xanthocera - Yellowhorn Fern-sawfly

Recorded fairly widely across England, in addition to one record in 1958 in Wester Ross. No confirmed Welsh record at time of writing, although one right against the border in Shropshire in 1993. Assessments against all criteria give no reason to consider it threatened, although the range may have contracted southwards slightly in recent years (Musgrove, 2023).

This species is very similar to Strongylogaster multifasciata. Strongylogaster xanthocera is the less common species.

Strongylogaster xanthocera males are more frequent than females, whereas males are rare in multifasciata. In the male the abdomen has the first tergite black right to the lateral margins and usually with at least the second tergite black also. Males of multifasciata have the first tergite marked with yellow on the lateral faces and the yellowing is greater on tergite 2.

Females of xanthocera have at least the first three antennal segments yellow, the epipygium is usually black and the hind femur is usually black almost to the apex. In multifasciata females, the third antennal segment is only partially yellow, the epipygium is usually brown and the hind femur is usually only black basally. The anal cells of the fore wing lack a cross-vein. The labrum is black. The sawsheath of the female is divergent at the apex.

The green larvae feed on bracken. The head is marked with black around the temples and there is a black mark on the anal segment.

Jump to other Strongylogaster species

Size: 8 - 11mm

GB IUCN Status: Least Concern
GB IUCN Status: None

Distribution: England, Scotland

Flight period: May to June

Plant associations: Pteridium aquilinum (bracken)

References:

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

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

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 Natural England, unpublished