Previously only known in Britain from one doubtful record from the 19th Century, this species was rediscovered in Surrey in 2016. It is an entirely black insect with the head and thorax shining with very fine punctures. Although normally black, the front of the fore and middle knees may be brownish or the entire front face of the foreleg paler.
Eggs are laid onto leaf petioles from where larvae bore into the stems of roses. Larvae bore upwards from the entrance hole, for a distance of up to 15cm, causing wilt (similar damage is caused by Ardis spp.).
Size: 6 - 8mm
Flight period: May to July
Plant associations: Rosa spp. (roses)
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
Halstead, A.J., 2018. Two stem-boring sawflies new to Britain, Janus compressus (Hym.: Cephidae) and Cladardis elongatula (Hym.: Tenthredinidae), British Journal of Entomology and Natural History, Vol 31(1), BENHS, Reading.
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