The limiting effect of host availability for the immature stages on population growth in economically important ixodid ticks.

Of 12 southern African species of ixodid ticks in which the adults are commonly parasitc on cattle, only 4 exhibited massive increases in abundance in the absence of dipping. It is suggested that host availability for the immature stages is the major factor limiting population growth in a given environment. The species showing large increases in abundance are those in which the immature stages are predominantly parasitic on cattle, whereas the species showing small to moderate increases in abundance are those in which the immature stages are parasitic on specific nonungulate hosts.