Rory McAllister missed a penalty and was sent off in the space of two first-half minutes as Peterhead were thumped 4-0 at home by fellow promotion hopefuls Ayr.Striker McAllister put his 10th-minute spot-kick against the left post after Ayr defender Nicky Devlin fouled Jordon Brown before seeing red for elbowing midfielder Peter Murphy.Ayr made the most of their numerical advantage in the 24th minute when forward Craig Moore converted Ross McCrorie's pass with a left-footed finish from the centre of the 18-yard box.Teenage defender McCrorie, on loan from Rangers, found the net with a close-range finish to double the lead on the stroke of half-time before on-loan Blackburn striker Jordan Preston curled his 13th goal of the season into the bottom-right corner nine minutes after the restart.Moore smashed his second goal of the game into the roof of the net nine minutes from time as United leapfrogged their opponents into second place with a comprehensive victory.