For a year beginning in Sept. 1954 the gullets of Hereford cattle from Oregon were obtained and examined for the presence of Hypoderma lineatum. Collections usually were made each month and a total of 558 was obtained. Peak of development appeared to be reached in Jan., at which time the maximum length of 16 mm was reached. The smallest larvae (2.5 mm) were found in July. None was found during Mar. through June.