In the late-1800's and early-mid-1900's there were a dozen or so performers-- all male-- who billed themselves as Spider-Boys. Most famous was probably Henry Bulson. These performers typically had withered legs and strong upper bodies, and were thus named for their spider-like style of perambulating on their hands with their useless legs bent out of the way. The cause of such may be Muscular dystrophy, or Polio (poliomyelitis).