Indigo Girls [ tickets ] have tacked more dates onto their in-progress US tour behind last year's "Poseidon and the Bitter Bug."

The itinerary, which begin late last month, continues with a March 17 performance in Missoula, MT, moving south along the West Coast before heading inland to the Midwest. Since last check, 16 new concerts have been added to the end of the schedule, now pushing the road trip into late May. Details are shown at right.

"Poseidon and the Bitter Bug," the folk-rockers' 11th studio effort, hit shelves last March. The two-disc release debuted at No. 29 on The Billboard 200 and marked the pair's first album on their own IG Recordings label.

For the latest release, the Indigo Girls teamed up again with producer Mitchell Froom, who produced the pair's 2006 album, "Despite Our Differences."

"Mitchell was able to build a bridge between Emily's songs and my songs more successfully than anyone we've worked with," Ray explained at the band's website. "He's a musician's musician and has a very clear idea of what will work."

In November, the Grammy-winning duo unveiled "Live at the Roxy," a concert DVD that captures the Girls' July 2007 show at Atlanta's Roxy Theater.

Ray, who started the not-for-profit label Daemon Records in 2004, has released four solo albums, the most recent of which is 2008's"Didn't It Feel Kinder."