Take the example of H. contortus in a hot climate, such as Queensland, where the rate of evaporation is high. Here 100 mm of precipitation per month may be required to provide sufficient moisture. So high temperatures inhibit development because evaporation is high. Conditions in spring and autumn are best for development. A wet summer is favourable but a dry summer too hot and dry.
Winter is usually too cold.
The eggs of some parasite species can develop in drier or cooler conditions than others. In fact it is largely the differences between parasite species in their tolerance to temperature and moisture that determine the distribution of parasites throughout the country. Survival on pasture The larval stages which occur between the egg and L3 stage are very vulnerable to environmental extremes. Neither egg or L3 stage can feed. When it is dry they desiccate.