Pycnogonum stearnsi or Stearns' sea spider is a marine arthropod in the family Pycnogonidae. It is found on north east Pacific Ocean,from British Columbia, to California, including Japan.
This spider-like animal grows to about 2.5 cm. The colour can be white, cream, sometimes pinkish. Stearns' sea spider is found under rocks or in dead barnacle shells. It sucking out fluids of the sea anemones Anthopleura sola, Anthopleura xanthogrammica, Metridium senile and Anthopleura elegantissima, the hydroids, Obelia and Aglaophenia and the sea squirt, Clavelina, but leaving the animal flaccid but alive.