A week after plundering 13 tries in an 85-5 win in Spain over Bizkaia Gernika in Pool Two, the Warriors made it an unlucky afternoon for the Italians as they added 14 more at Sixways on Saturday.
Lemi weighed in with two tries in each half to equal All Black wing Rico Gear's club European record against GRAN Parma four seasons ago, but his 20 points were beaten by outside half Joe Carlisle.
Seven days on from notching 20 points in Spain, Carlisle eclipsed Shane Drahm's club European record of 21 points in a match against Montauban four years ago as he ended with a match haul of 30 from 10 conversions and two tries.
The Warriors will find their next two games a different prospect, however, as they chase a second Amlin Challenge Cup final berth.
Their next two assignments are against Top 14 side Perpignan, who scored 10 tries in their 79-12 away win in Rovigo ahead of their home clash with the Spanish champions in round two.
Warriors will have home advantage in the first of the back-to-back games on Thursday, December 6.
Wing Andy Short also helped himself to a hat-trick against Rovigo and England Under-20 back-rower Matt Kvesic scored twice.
London Irish made it a perfect 10 points out of 10 in their opening two games in Pool One with a 69-26 home win over Mont-de-Marsan. There were 11 tries to add to their six in France the previous weekend as they made it back-to-back wins over Top 14 clubs.
Having picked up 11 points in the 43-16 win at Bordeaux-Begles in Round 1, outside half Ian Humphreys helped himself to 13 more at the Madejski Stadium.
The home side had clinched their bonus point by half-time, when they led 24-12, and romped home after the break to end the day one point clear of English Premiership rivals Gloucester at the top of the Pool table.
Those two teams will meet in the back-to-back games in rounds three and four in December, with Gloucester having home advantage in the first meting at Kingsholm on Friday, December 8.
London Welsh got their first win in Europe in Pool Five as they beat Cavalieri Prato 32-31.
The home side emerged with two points after scoring four tries, but a brace from wing Joe Ajuma and another try from hooker Dan George allowed the Exiles to pick up the major points.
Having led from the 11th minute, when George crashed over for his try, Lyn Jones' side then conceded two quick-fire tries in the space of six minutes to lose the lead for the first time on 76 minutes at 31-29.
But full-back Alex Davies stepped up to fire over a 45-metre penalty two minutes from time to clinch the win.
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