The Umigga were a yellow skinned, large eyed species. First contact was made in 2341 when a group of cadets from the USS Republic moved their space station out of harms way in the Beta Arantialus system. Exposure to the radiation in that system was causing these people to change into vicious lizards. They were quite thankful. The male can produce a large electrical charge, but males make up only one tenth the population. (TNG novel: Secret of the Lizard People)