LIFE-CYCLE OF CRENOSOMA-PETROWI (NEMATODA, METASTRONGYLOIDEA) FROM BLACK BEARS (URSUS-AMERICANUS)

First-stage larvae of Crenosoma petrowi Morozov, 1939 from feces of bl ack bears (Ursus americanus) developed to the third stage in the gastr opod Mesodon thyroidus. In snails held at 23.5 degrees C, the first an d second moults occurred on days 6-7 and 9-11, respectively, after inf ection. The prepatent period of C. petrowi was 19-25 days in five expe rimentally infected black bears. Both times of first and second moults and the prepatent periods are similar among species of Crenosoma. Cre nosoma petrowi did not produce patent infections in, and no nematodes were recovered from, experimentally infected striped skunks (Mephitis mephitis), raccoons (Procyon lotor), or red foxes (Vulpes vulpes).