The Glasgow Warriors scrum-half has been confirmed as skipper, with the rest of the team due to be announced on Thursday.
Scotland head coach Vern Cotter has named a 25-man squad to face Ireland, chosen from the initial 47-player pool selected to take part in the warm-up test series.
The 22 players who miss out on the match against Ireland will remain in Edinburgh and continue preparations at Murrayfield.
Along with Pyrgos, Cotter has named Dougie Fife, Sam Hidalgo-Clyne, Peter Horne, Ruaridh Jackson, Sean Lamont, Tommy Seymor, Greig Tonks, Richie Vernon, Tim Visser and Duncan Weir as his backs, while John Barclay, Hugh Blake, Fraser Brown, Blair Cowan, Mike Cusack, David Denton, Allan Dell, Grant Gilchrist, Ryan Grant, Jim Hamilton, Rob Harley, Stuart McInally, Gordon Reid and Jon Welsh make up the forwards.
There are four potential new caps in Black, Cusack, Dell and McInally.
The Ireland fixture is the first of four warm-up internationals which Cotter will use to assess his group before slashing an extended 47-man squad to his final list of 31 on September 2.
Scotland will also take Italy in Turin on August 22 and again at Murrayfield on August 29 before travelling to Paris to take on France on September 5.
Scotland take on Japan in Gloucester in their opening Pool B match on September 23.