The ecology of the free-living stages of Ostertagia circumcincta

Callinan A. P. L. 1978. The ecology of the free-living stages of Ostertagia circumcincta. Internationaljournal for Parasitology8: 233–237. The development and survival of the free-living stages O. circumcincta was studied in western Victoria in 1974–1976. For all plots in which development occurred, pre-infective larvae (L₁-L₂) were recovered within 0–8 days, infective larvae (L₃) within 7–30 days and L₃ on herbage and soil within 4–27 days. The mean minimum development time to L₃ on herbage and soil was 14·3 ± 3·5 days and the mean development time to maximum yield of these was 33·3 ± 6·3 days. There were no distinct differences in development rates between plots. Plot yields of L₃ on herbage and soil varied inversely as the mean of daily temperatures for the period until maximum yield of these. Yields varied from 0 to 16% of the number of eggs put out on each plot and highest yields were obtained from eggs put out during late autumn-winter. No L₃ were observed to survive over summer. The migratory habits of L₃ were such that a mean of 75·1 ± 5·6% of L₃ on herbage and soil were actually on herbage; the soil was always a significant source of L₃.