Pseudorhyssa alpestris (Holmgren, 1860)

Verheyde, Fons, Hoekstra, Paul, Libert, Pierre-Nicolas, Meijer, Hilco, Ketelaere, Augustijn De, Vandaudenard, Thibaud, Belgers, Dick & Brosens, Edwin, 1880, Two hundred and five ichneumonid wasps reported for the first time in Belgium and the Netherlands (Hymenoptera: Ichneumonidae), Belgian Journal of Entomology 122, pp. 1-142 : 103-104

Pseudorhyssa alpestris (Holmgren, 1860)

Pseudorhyssa is a very distinctive genus consisting of giant species with conspicuous transverse rugae on their mesoscutum (and thus closely resembling Rhyssinae ). In contrast to this subfamily the occipital carina is complete medio-dorsally and the fore wing vein 1cu-a is situated opposite of M&RS (BROAD et al., 2018). Both species reported here are migratory and only recently colonized the Low Countries, coming from central and eastern Europe (see also VERHEYDE et al., 2020a). The genus was recently transferred from the subfamily Poemeniinae to Pimplinae ( KLOPFSTEIN et al., 2018) .

P. alpestris has red hind coxae and the first two tergites usually have a smooth reddish triangle apically ( VARGA, 2015). It is mainly associated with and found on hardwood, where it acts as cleptoparasitoid of for example Rhyssella approximator (Fabricius, 1793) , an ichneumonid wasp which belongs to the abovementioned subfamily of Rhyssinae (HILSZCZANSKI, 2018) .

First report of the species and the genus for Belgium and the Netherlands.

MATERIAL EXAMINED:

BELGIUM: • 1 ♀; Oud-Turnhout , Landschap De Liereman (AN); 51°20’28”N 5°00’27”E; 18/v/2020; N. Van Loco leg.; field observation, oviposition on Betula sp. ; F. Verheyde det. (ObsID: 204102351) . • 1 ♀; Kasterlee , De Tikkebroeken (AN); 51°16’59”N 4°59’58”E; 3/vi/2020; N. Van Loco leg.; field observation, oviposition on Betula sp. ; F. Verheyde det. (ObsID: 191279896) .

THE NETHERLANDS: • 1 ♀; Tilburg , Leijbos (NB); 51°32’35”N 5°00’52”E; 23/iv/2020; KNNV Tilburg leg.; coll . PH; malaise trap (16-23); P. Hoekstra det. (ObsID: 203450372) • 1 ♀; Sint-Michielsgestel (NB); 51°39’29”N 5°19’34”E; 7/vi/2020; M. Heymans leg.; field observation; F. Verheyde det. (ObsID: 195616765) .