Nysson interruptus (Fabricius,1798)

Synonyms

Ceropales spinosus Fabricius, 1804; Nysson panzeri Lepeletier, 1845; Nysson shukardi Wesmael, 1852

Description and notes

The rarest of our four Nysson species, with British populations seemingly using a different host to those in Fennoscandia. It is similarly threatened in Germany.

Distribution

The distribution of this wasp has changed dramatically, there are no modern (post 1990) records from its former localities along the south coast, and many of these are from the first quarter of the 20th Century. The record from West Sussex is known to have been a mistake, leaving O.W. Richard’s 1925 Oxshott, Surrey record as the only inland site, pre 1990. Older records from the Channel Islands have been repeated post 1990, so the situation here is unchanged. The big change is the cluster of well-supported records towards the north of East Anglia, predominately Norfolk. The presumed host, Argogorytes fargei, has been recorded in this area on a number of occasions since 1939, but with a concentration of records post 1990. Whether this situation reflects a real change in the distribution, or just a change in the distribution and activity of recorders, several BWARS Members are very active in this formerly poorly covered area, is not clear.

Abroad, recorded from most European countries and Asia Minor (Lomholdt, 1975-76).

Status (in Britain only)

Listed as Vulnerable (RDB2) by Falk (1991).

Habitat

Presumed to resemble that of its host, with soft rock cliffs, coastal landslips and heaths featuring strongly in British data. The host is particularly reliant on vertical earth banks or sparsely vegetated slopes for nesting. Adults have been reported flying round bramblebushes, but not settling.

Flight period

Late May to early August.

Flowers visited

Various umbellifers and bramble (Rubus); also scabious (Knautia and Succisa) in Fennoscandia, and yarrow (Achillea millefolium) and stonecrop (Sedum sp.) in France (Bitsch et al, 1997).

Parasites

No information available.

Parasitic biology

Nysson interruptus is clearly the special cleptoparasite of Argogorytes fargei, with much data to support this including an observation of the Nysson entering an A. fargei nest in Devon (Perkins, 1923). In Fennoscandia, Lomholdt cites Gorytes quadrifasciatus and the non-British G. quinquecinctus as hosts with no mention of A. fargei.

Author of profile

S J Falk & M E Edwards

Year profile last updated

2019