Biarritz blitzed Glasgow during the second half in France
Biarritz (11) 41
Tries: Coetzee, Ngwenya Cons: Courrent 3 Pens: Courrent 5
Glasgow (13) 20
Tries: T Evans, Cusiter Cons: Parks 2 Pens: Parks 2
Biarritz clinched a home tie in the Heineken Cup quarter-finals following a second-half demolition of Glasgow.
Warriors led 20-11 early in the second half following scintillating tries from Thom Evans and Chris Cusiter.
But Biarritz rallied with 30 unanswered points and clinched a crucial bonus point 50 seconds from the final whistle to guarantee home advantage.
Eduard Coetzee and Takudzwa Ngwenya crossed before Ilikena Bolakoro followed a penalty try to score again.
Biarritz had already reserved their place in the quarter-finals after winning four of their previous pool games, but they were without key playmakers Dimitri Yachvili and Damien Traille through injury while fly-half Julien Peyrelongue was rested.
It was Peyrelongue's replacement, Valentin Courrent, who stepped up to open the scoring in the fourth minute with a penalty, but Glasgow managed to handle the muddy conditions well early on.
Flanker John Barclay hammered a hole through the heart of the Biarritz defence, but it was the vision of Chris Cusiter that created the first try.
The Scotland scrum-half found Evans out wide in open space with an intelligent kick and the flying wing easily went past prop Mosese Moala before scooping up possession and diving over despite Bolakoro's lunge.
Dan Parks expertly guided his conversion through the posts from close to the touchline for a surprise 7-3 lead.
That advantage soon grew as Glasgow dominated the close-quarter exchanges.
Second-row forward Richie Gray's charge led to a second Parks penalty and a neat interchange of passes between Max Evans, John Beattie and Cusiter ended in a third as the visitors stunned the partisan home crowd by leading 13-3.
That sparked a change in tempo and tactics from Biarritz that reduced the deficit to 13-11 by half-time.
Courrent kicked a 28th-minute penalty but was off target five minutes later and he missed again after prop Coetzee was shoved over the line by the rest of the Biarritz pack three minutes before the break.
The second half got off to a tremendous start for Glasgow, despite Parks missing for the first time, with a contender for try of the season.
Full-back Bernardo Stortoni launched an audacious attack with a quickly taken penalty just 10 metres from the Glasgow try-line and it ended with Cusiter sliding between the Biarritz posts.
Stortoni burst from defence and exchanged passes with Max Evans before handing Cusiter a 25-metre dash to score.
Parks' conversion moved Glasgow 20-11 ahead after 48 minutes, but that was to be the last time they had any grip on the tie.
Biarritz turned their fortunes around in the scrum, with replacement Kiwi prop Campbell Johnstone having an impact and, with more firepower following off the bench, that dominance up front led to 30 unanswered points.
Courrent drew Biarritz level with three successive penalties before wing Ngwenya made light work of Hefin O'Hare's flapping attempt at a tackle to race clear for a try that put the hosts ahead for the first time since the 10th minute.
The home side's advantage in the scrum forced referee Dave Pearson to award a penalty try after 69 minutes, but it took until the last minute of the game before they clinched the vital bonus point when Bolakoro raced on to Imanol Harinordoquy's break to score.
Biarritz: Couet-Lannes, Ngwenya, Mignardi, Tranier, Bolakoro, Courrent, Lesgourgues, Coetzee, August, Moala, Thion, Taele-Pvihi, Lund, Hall, Harinordoquy.
Replacements: Balshaw for Couet-Lannes (66), Hunt for Lesgourgues (54), Hughes for Coetzee (71), Terrain for August (71), Johnstone for Moala (45), Carizza for Taele-Pvihi (67), Alaxndre for Hall (70). Not Used: Erinle.
Glasgow: Stortoni, Dewey, M. Evans, Morrison, T. Evans, Parks, Cusiter, Welsh, Hall, Low, Gray, Kellock, Brown, Barclay, Beattie.
Replacements: O'Hare for Dewey (56), Jackson for Parks (64), McMillan for Cusiter (65), Tkachuk for Welsh (61), Thomson for Hall (59), Turner for Low (41), Eddie for Beattie (59). Not Used: Kalman.
Ref: Dave Pearson (RFU)