Abstract
Various authors have recorded the seasonal occurrence of different species of nematode parasites in sheep. Some of these (Ross & Gordon, 1936; Gordon, 1950; Taylor, 1934) have been mainly interested in the epidemiology of outbreaks of parasitic disease, but others have recorded the incidence of different species in flocks in which no outbreak has occurred (Gordon, 1948, 1950; Morgan & Oldham, 1934; Morgan & Sloan, 1947; Morgan, Parnell & Rayski, 1950; Parnell, 1954; Parnell, Rayski, Dunn & Mackenzie, 1954; Stewart & Douglas, 1938; Tetley, 1935, 1941, 1949; Wilson, Morgan, Parnell & Rayski, 1953).