As with all Tenthredopsis species Tenthredopsis friesei is variable in colour. The description given here follows Blank and Ritzau 1998 but it should be noted that British specimens may differ in colour from continental counterparts.
In the female the head is usually extensively pale, and the pronotum with a pale posterior margin. The basic body colour is black. Mesoscutum predominantly black and the abdomen black with red segments. The abdomen has the sixth tergite, at most, basally slightly red on the lateral faces. The middle areas of the second and third tergites have a fine microreticulation giving them a silky sheen. Tergites three to five are red. The clypeus is yellow, darkened at the base and lighter apically. The hind tarsi are yellowish-white, or less often, light brown with the base of the first tarsal segment and the apex of the fifth segment usually significantly darkened. The hind coxae are mostly completely black but occasionally slightly lightened apically on the outer face. In the male the mesepisternum and pectus are all yellow. The eighth tergite on dried specimens has a longitudinal keel on the midline that does not reach the base of the tergite. On either side of the keel is a transverse oval depression that extends from the posterior margin to the center of the tergite. The hind tarsi are yellowish-white, with the base of the first tarsal segment and the apex of the fifth segment usually significantly darkened.
Larvae feed on grasses.
Size: 11 - 12mm
Status: Data deficient
Distribution: England, Scotland
Flight period: May to June
Plant associations: Gramineae (grasses)
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Blank, S.M. and Ritzau, C., 1998. Die Tenthredopsini Deutschlands (Hymenoptera: Tenthredinidae). Pflanzenwespen Deutschlands (Hymenoptera, Symphyta). Kommentierte Bestandsaufnahme, pp.227-246.
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