They're called "wolf" spiders for good reason. They are ground dwelling spiders that do not rely on a web for capturing food, but instead use their hunting skills to find and run down their prey like, well.....a wolf. This particular female looks as if she’s dragging a rock behind her, but is in fact an egg sac. After mating with a male the female lays her eggs, fertilizes them with the male’s sperm that has been stored in her body, and then builds a silken sac around them. She is very maternal and will protect the egg laden sac with her life. It will be carried from her spinneret for a week or two as they develop and then she’ll pierce the egg sac with her fangs allowing the young to escape. The spiderlings will then climb upon her back for a short period of time before dispersing to begin a life of their own.