Monsoma pulveratum (Retzius, 1783)

Monsoma pulveratum

An easily recognisable species. Predominantly dull black on the thorax and abdomen with broad white lateral margins to the tergites. The legs, pronotal margin, tegulae and sometimes the margins of the tergites suffused with peach and orange. The stigma is pale in contrast to the swollen apex of the costa which is dark. The male is darker but very rare.

Monsoma pulveratum larvae feed on alder and willows initially creating round holes in the leaf blade, eventually consuming the whole leaf. Young leaves are preferred. Females can begin laying early in the year provided the air temperature is above 20'C (Pieronek, 1980). Eggs are laid in incisions cut into the leaf blade between lateral veins. Egg development lasts one to two weeks. Larvae have 5 or 6 instars. All instars are similar in appearance being coloured light blueish green without noticeable markings. The torso is not conspicuously segmented. As the larva develops a white waxy coating forms on the dorsum and laterally with this coating becoming more pronounced at maturity. Prolegs are present on abdominal segments two to eight and ten. The head is coloured as the torso. Eonymphs tunnel into pith or loose bark for overwintering.

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Size: Approx. 9mm

Status: Common

Distribution: England, Scotland, Wales, Ireland

Flight period: May to June

Plant associations: Alnus glutinosa (alder), Alnus incana (grey alder) and salix spp. (willows)

References:

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

Pieronek, B., 1980. On the larval Monosoma pulverata (Retzius) feeding on alder (Hymenoptera: Tenthredinidae-Blennocampinae). Mitteilungen aus dem Zoologischen Museum in Berlin, 56(2), pp.195-199.