Candidates in the party primaries for the vacant Fifth Congressional District seat have been invited to participate in a public forum from 2 to 4 p.m. Sept. 29 at Wayland Middle School, 201 Main St. The free event is being sponsored by Leagues of Women Voters organizations in Sudbury, Wayland and Weston. Ten candidates have qualified for the ballot in the Democratic and Republican primary election scheduled for Oct. 15. The final election for the US House seat will be Dec. 10. The district had been represented by Edward Markey, who was elected to the US Senate in June. Full story for BostonGlobe.com subscribers.