Studies on the ecology of the tick Amblyomma hebraeum Koch in the Eastern Cape Province of South Africa. II. Survival and development.

Quantitative data are given on the survival and rate of development of Amblyomma hebraeum Koch in relation to temperature and humidity, in laboratory and field conditions. By comparison with other ixodid species the developmental periods of A. hebraeum are extremely long. Development is most rapid at 30 C, and the duration of the developmental periods increases exponentially with decreasing temperature. Oviposition occurs successfully at 15 and 30 C, egg incubation at 20 to 30 C, and larval and nymphal molting at 15 to 35 C. The ability of the developing stages to survive in dry conditions increases with increasing size, i.e. from egg to engorged larva. Mortality in the developing stages increases at low humidities as temperature decreases, due to the longer periods over which water is lost. The conversion efficiency of ovipositing females is influenced by both temperature and atmospheric humidity. Longevity of unfed larvae is correlated directly with saturation deficit. Longevity of unfed nymphs and adults is dependent on both temperature and saturation deficit.