Ruan Pienaar will represent the Barbarians against England at Twickenham on 28 May.
The former Springbok scrumhalf will then line up against the famous invitation club in his final appearance for Ulster at the Kingspan Stadium in Belfast on 1 June.
Pienaar will be joined at the Baa-Baas by New Zealand fullback Charles Piutau (Ulster), England flank Steffon Armitage (Pau), Samoa lock Joe Tekori and France centre Yann David (both Toulouse).
The latest call-ups take the number of players at coach Vern Cotter’s disposal to 14 with more invitations to follow, particularly for the key flyhalf role.
Backs: Bundee Aki (Connacht), Adam Ashley-Cooper (Bordeaux Begles & Australia), Yann David (Toulouse & France), Will Genia (Stade Francais & Australia), Ruan Pienaar (Ulster & South Africa), Charles Piutau (Ulster & New Zealand)
Forwards: Patricio Albacete (Toulouse & Argentina), Steffon Armitage (Pau & England), Thierry Dusautoir (Toulouse & France), Corey Flynn (Glasgow Warriors & New Zealand), Facundo Isa (Lyon & Argentina), Census Johnston (Toulouse & Samoa), Joe Tekori (Toulouse & Samoa), Jeremy Thrush (Gloucester & New Zealand)
Photo: Ramsey Cardy/Getty Images