First, a bit of biology. Crayfish (aka crawfish, crawdads, crawls, ditch lobsters, and mud bugs) are common in streams and lakes throughout the country and live a rather short life--usually less than two years. They have a hard exoskeleton, which is great for protection but must be shed in order for the crayfish to grow. This shell is molted up to 10 times each growing season, with May through August being prime times, depending on where you live. It takes a couple of days for the new shell to harden.