This time last year the conservative southern Democratic members of Congress known as "Boll Weevils" were telling the House Democratic leadership where to head in, voting to enact President Reagan's economic program and being invited to join the Republican Party by northern colleagues who thought they should be ashamed of themselves.

Ashamed? So unashamed are the unregenerate rebels that they have formed a political action committee to help elect more conservative Democrats and, in their view, improve the party. It's that great American tradition of working within the system--it's better to be inside spitting out than outside spitting in.

"We want to working within the party to rebuild it," says Rep. Charles W. Stenholm (D-Tex.), a founder of the 40-member Conservative Democratic Forum, as the Boll Weevils prefer to be known. "The national party has come under the domination of a small group of liberals who are out of sync with the direction of the political movement in the country."

The Weevils plan a fund-raising dinner in early June and have vowed to go anywhere, anytime, to campaign for conservative Democratic House candidates. The exception, as a gesture of party loyalty, is that they won't support anyone challenging an incumbent Democrat, however liberal, for nomination. Non-Weevils appear to welcome their action. "As long as they vote to organize the House as Democrats in 1983, that's fine with me," says Rep. Tony Coelho (D-Calif.), chairman of the Democratic Congressional Campaign Committee.