Euura triandrae (Benson, 1941)

Euura triandrae - proxima group (formerly Pontania triandrae )

See Liston et al (2017) for determination of adults. Males are rare. There is some doubt as to whether this is in fact a species separate to Euura proxima. The females are not morphologically distinguishable from proxima.

Euura triandrae larvae feed on almond willow causing coffee bean shaped galls that transect the leaf blade but grow more on the upper surface. The galls are similar to Euura proxima but both species are faithful to their host plant. Therefore, identification of the willow plant is essential in separating the galls from proxima. Single, or very few galls per leaf. The galls are green becoming dark red or brownish above, yellow-green below, and with a smooth surface.

Size: Female: 2.9 - 4.5mm, male: not assessed

Status: Local

Distribution: England, Scotland, Ireland

Flight period: Bi- or multivoltine

Plant associations: Salix triandra (almond willow)

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.D., Heibo, E., Prous, M., Vårdal, H., Nyman, T. and Vikberg, V., 2017. North European gall-inducing Euura sawflies (Hymenoptera, Tenthredinidae, Nematinae). Zootaxa, 4302(1), pp.1-115.

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