In each of the past four years, 1,000 or more immigrant children who arrived at the southern U.S. border without their parents have reported being sexually abused while in government custody, according to federal records released Tuesday.

Thursday at the Vatican, Pope Francis stood before some 200 participants in an unprecedented summit on preventing clergy sex abuse and said Catholics are seeking not simply "condemnations" but "concrete, effective measures."

But a crisis that has crossed borders and generations, lacerating the church and shaking the pope's credibility, is standing in the way as he seeks to forge a path ahead.

Updated at 6:40 a.m. Friday

You might think the world's biggest bee would be easy to find. But that's not the case: Until recently, the last time anyone had reported seeing a Wallace's giant bee living in the wild was in 1981. That changed in January, when the rare bee was spotted on an island of Indonesia.