According to Prous et al, 2019, there is currently no reliable key or species treatment available for this genus. The description follows Benson.
The body is mainly yellow with the head, upper surface of antennae, middle of the pronotum, the mesonotum and the metanotum black. The wings are yellowish basally. The stigma is brown with darker margins, the costa yellow and the rest of the venation brown to piceous.
Larvae of Cladius grandis feed gregariously on poplars and willows.
Size: 7 - 9mm
Distribution: England, Scotland, Ireland
Flight period: Bivoltine, May to August
Plant associations: Populus spp. and Salix spp. (poplars and willows)
The National Biodiversity Network records are shown on the map below. (See terms and conditions)
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
Prous, M., Liston, A., Kramp, K., Savina, H., Vårdal, H. and Taeger, A., 2019. The West Palaearctic genera of Nematinae (Hymenoptera, Tenthredinidae). ZooKeys, 875, p.63.