The former Mansfield striker put his team into a 27th-minute lead and then Wayne Allison punished a dreadful error to put the home side in control.
Shane Nicholson wrapped up a convincing victory with a late free-kick and the damage could have been worse,but for a good save from Gareth Stewart at the end.
Bournemouth had started well and might have gone on to dictate the game if James Hayter had not squandered the sort of opening he normallytputs away.
A cross rom Andrew Surman was knocked back across goal and Hayter was unmarked six yards out but put his shot straight at keeper Barry Roche. It was a bad miss, and strike partner Dani Rodrigues should have done better than fire over the bar after beating two defenders in the 16th minute.
Larkin showed how to finish in the 27th minute when Allison knocked a long ball into his path and the Irishman drilled a right-foot shot past Stewart from 15 yards.
Bournemouth left themselves in deep trouble in the 53rd minute, when Stephen Cooke was caught in posession by Larkin on the edge of his own penalty area and Allison made no mistake with a shot across the helpless Stewart.
Roche did well to deny Hayter again, and pushed away a curlking shot from Surman, but Bournemouth were always chasing the game.
They brought on Steve Fletcher but Chesterfield settled any arguments with a Nicholson's free kick in the 78th minute that was curled around the defensive wall.
Bournemouth never came to terms with the more muscular approach of Chesterfield, and on the evidence of this performance, badly need some of their injured players back in contention.