EURA PROXIMA GROUP
Euura triandrae - Almond-leaved Bean-galler
Pontania triandrae Benson, 1941
North to southern Scotland. Not morphologically separable from Euura proxima. Liston et al. (2017) retain as a species but express strong reservations as to the validity of this. Additionally, probably under-recorded as identification rests solely on the correct identification of the host tree, and many cases may well be mistakenly named as the ubiquitous proxima (Musgrove, 2024).
See Liston et al (2017) for determination of adults. Males are rare. Within this group, males of Euura proxima, bridgmanii and triandrae cannot be separated and the females of triandrae 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.
Jump to other group proxima species
Size: Female: 2.9 - 4.5mm, male: not assessed
GB IUCN status: Least Concern
GB rarity status: None
Distribution: England, Scotland, Ireland
Flight period: Bi- or multivoltine
Plant associations: Salix triandra (Almond Willow)
The National Biodiversity Network records are shown on the map below. (See terms and conditions)
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- Euura triandrae gall Credit Andrew Green
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- Euura triandrae gall Credit Andrew Green
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- Euura triandrae larval gall on Salix triandra Credit Dave Gibbs
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- Euura triandrae larval gall on Salix triandra Credit Dave Gibbs
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
Musgrove, A.J. 2024. A review of the status of sawflies of Great Britain - Phase 3: The Tenthredinidae (subfamily Nematinae). Natural England, unpublished