Widow

This is a small ass spider jeez

Cannot be captured. They have a radioactive variant. Can also spawn Spider Silk background walls, which can be destroyed to produce the Spider Silk item, which in turn could potentially be exploited if you can make an area big enough to avoid them while mining the silk, but you never heard that.

SpawnID: bighairyfrankbaby

Special thanks to ExToRtIoN NuKeZ for providing details on this spider.