The "Black widows" of Dagestan: Female suicide bombers on the rise in Russian republics

As the Boston bombing investigation focuses on the Tsarnaev brothers' possible terror ties to Dagestan and neighboring Chechnya, one disturbing trend in that part of the world is the rise of women suicide bombers.

They're known as "black widows" and named that way because many are wives of insurgents killed by government forces.

Nic Robertson is in Dagestan with our OutFront investigation.