Looking for more information, I found some historical, artistic, and other information about the Warega. This website presented a mask from "Lega (Balega, Rega, Walega, Warega), Democratic Republic of the Congo" with the following explanation --
The 100,000 Lega inhabit the forest region in eastern DRC. They do not possess a centralized political organization, and both men and women aspire to moral authority by gaining high rank in the bwami initiation association. The highest ranking members of the bwami association own, use and interpret all Lega sculpture. Many categories of objects, including masks are used in connection with the association’s activities. Wooden masks with heart-shaped, concave faces painted with white pigment are owned, in some areas, by every male member of the most advanced level of the second highest grade of the bwami association. These masks are not worn over the face. Participants in most rites display their masks as a group in conjunction with particular dance movements and aphorisms, which vary depending on the context in which they are used. In some rites they may be held in the hand, in others they may be fixed to hats or arranged on a miniature palisade.
I have seen some of this information in other sources also -- particularly about the way the masks are carried or displayed, not worn. Also, the masks are associated with protection from sorcery.
The history of the Lega as well as many more photos of masks is given here:
In the 16th century the Lega began their long migration from modern day Uganda into their present location. They were a warlike people whose fierceness inspired those, with whom they came into contact, to adopt many Lega customs. In the 17th century they attacked the Rwandan outpost of Rutshurer on their way to Maniema, just west of Lake Tanganyika, dividing and conquering the people who lived in the region. Many cultural traits have been assimilated into the surrounding cultures, and the Lega still dominate the region today.My earlier posts about our African masks are: Our African Masks, Why do I like African masks?, Masks, African Masks, and One more Art Fair trip. The most comprehensive website that I have found for studying African tribes and their art is: African Art Museum.