Cytisogaster genistae (Benson, 1947)

Cytisogaster genistae

One of three small species formerly included in the Rhogogaster picta group. All three have bicolorous blue-green/black stigma. Cytisogaster genistae is either parthenogenic or the males are indistinguishable from other species. The hind tibia are lined with black on the anterio-dorsal face. Facial markings and saw teeth are diagnostic (see Benson).

Larvae feed on broom and dyer's greenweed. Eggs are lain in a pocket on the upper surface of a leaflet. Larvae nibble the edges of the leaves. The larvae drop from the leaf when disturbed. There are typically four instars in total lasting 20 to 30 days. According to Chambers, after the final moult the larvae may remain on the plant for several weeks before entering the soil where they overwinter without forming any cocoon.

Size: 6 - 8.5mm

Status: Common

Distribution: England, Scotland, Wales

Flight period: May to July

Plant associations: Cytisus scoparius (broom), Genista tinctoria (dyer's greenweed)

References:

Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London

Chambers, V. H. 1950: The larvae of the Broom Sawflies Rhogogaster picta Klug and R. genistae Benson (Hym., Tenthredinidae). - The Entomologist's Monthly Magazine, Fourth Series, London 86(11): 117-120

Chambers, V. H. 1951: The larva and foodplant of Rhogogaster chambersi Benson (Hym., Tenthredinidae). - The Entomologist's Monthly Magazine, Fourth Series, London 87(12): 202-205

Chambers, V. H. 1952: A postscript upon Rhogogaster (Hym., Tenthredinidae). - The Entomologist's Monthly Magazine, Fourth Series, London 88(13): 62

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