Euura bergmanni (Dahlbom, 1835)

EUURA BERGMANNI GROUP

Euura bergmanni  - Bergmann's Willow Nematine

Nematus bergmanni Dahlbom, 1835
Nematus betulinus Dahlbom, 1835
Nematus virescens Hartig, 1837
Nematus betulinus Dahlbom in Brischke, 1850
Nematus curtispina Thomson, 1871
Nematus varipictus Holmgren, 1883
Amauronematus longicornis Konow, 1897
Pteronidea vernalis Lindqvist, 1937
Nematus macrocerus Hartig, 1840

Taking records at face value, this species is widespread north to northern Scotland. This species has been widely recorded, mostly using Benson (1958). A more updated treatment, backed by DNA studies, is given by Prous et al. (2021) but this will not have been used for most determinations. It is not entirely clear at present how many former determinations of bergmanni would still map to the taxon sensu Prous et al. (2021). The latter reference does confirm the taxon to be British. The lack of respondens within Benson's key will likely have resulted in at least some over-recording of bergmanni (depending on when the former arrived in Britain). Conversely, some male bergmanni are likely to have been named previously as viridis, as Prous et al. (2021) note that Benson's illustration of the male penis-valve of viridis actually relates to bergmanni (as does that titled for that species) (Musgrove, 2024).

Females are similar to Euura sylvestris and the oligospila group though the head is more rectangular in dorsal view. Specimens need to be determined by reference to the saw or penis valve. The background colour is usually green in life but may be yellow on occasion. The female is very variable in the amount of black on the body with spring and northern specimens sometimes almost entirely black on the thorax and abdomen. The summer generations exhibit more green colouration. In the summer generation females there is often an anchor-shaped dark mark on the otherwise green scutellum but the scutellum may be entirely green. The ocelli are black but the area posterior to the ocelli is predominantly green often with a black longitudinal line central to the postocellar area.

The male has the mesopleura mostly pale and the inner eye orbits are yellow or white. The malar gap is 1 to 1.4 times the diameter of the front ocellus.

Euura bergmanni larvae are slender and green with a white dorsal stripe, a pale head with a vertical brown stripe through each eye. They feed on various willows. Summer generations develop rapidly and spin a silken cocoon in leaf axils and growing tips. They remain in the cocoon for as little as one week.

Jump to other Euura bergmanni group species

Size: Female: 6 - 8mm. Male: 5 - 6mm.

GB IUCN status: Least Concern
GB rarity status: None

Distribution: England, Scotland, Wales, Ireland

Flight period: Multivoltine, April to September

Plant associations: Salix spp. (willows)