On a windy night in the west of Ireland, Connacht were hoping to provide a winning send-off for departing head coach Eric Elwood with the match also marking the final outings for the province of Johnny O'Connor, Adrian Flavin and the Leinster-bound Mike McCarthy.
However, a Ruaridh Jackson penalty was added by a Van der Merwe try as the visitors established a 10-3 half-time advantage with Dan Parks nailing a late penalty for Connacht.
Elwood's charges battled bravely on the restart with the wind at their backs, but the benefit of a strong replacements bench was vital for Glasgow as five points from the boot of another Lion Stuart Hogg, allied to Maitland's 70th-minute effort, eased them over the line.
Edinburgh posted only their seventh win of the season when they saw off Dragons 31-24 at Murrayfield in the final match of their RaboDirect PRO12 campaign.
Edinburgh had looked to be cruising when they entered the final quarter with a 31-10 lead after tries from Greig Tonks, Greig Laidlaw and Netani Talei, with Laidlaw kicking the rest of the points.
However, Dragons, who had led through an early try from Steffan Jones, profited from some poor defending and a wayward pass that produced late tries for Dan Lydiate and Tom Prydie, who contributed the rest of his side's points with the boot. The defeat leaves Dragons second from bottom in the league table - one place behind Edinburgh and with only Zebre below them.
The Scarlets crashed to an embarrassing four tries to one 41-17 defeat to Treviso at Parc y Scarlets but still managed to book their place in the RaboDirect PRO12 end of season play-offs.
The region sealed a semi-final shot against Ulster in Ravenhill next Friday after their Welsh rivals the Ospreys went down 37-19 in Leinster.
Treviso were celebrating their first double over Scarlets with tries for No 8 Robert Barbieri, flanker Monoa Vosawai, replacement centre Luca Mosari and wing Christian Loamanu. Outside-half Kris Burton kicked 21 points.