The investigations submitted in this thesis comprise an intensive study of the effect of flooding of pasture and related phenomena on the Australian cattle tick, Boophilus microplus; and a general study of the seasonal incidence of ticks infesting cattle in south-east Queensland.
The flooding of pasture was investigated to assess the importance of this as a factor influencing cattle tick populations. A second motive for the study was to account for the differing results of previous authors in both laboratory and field investigations into flooding. During this investigation emphasis was placed on developing a quantitative approach to the study of tick ecology.
The results showed that while the eggs, free-living larvae and the parasitic stages of B. microplus were resistant to long periods of heavy rain, the engorged females were susceptible. The flooding of pasture may therefore be an important age-specific mortality factor; but the overall result of long periods of rain would be to provide favourable conditions for reproduction and so lead to an increase in the sizes of subsequent populations.
The study, on the seasonal incidence of ticks was carried out in two dissimilar habitats representing high and low altitude environments in south-east Queensland. In the high altitude area the seasonal incidence of three species of ticks infesting cattle was determined. The species studied were B. microplus, Haemaphysalis longicornis and Ixodes holocyclus; a major difference in their life cycles was found to be in their different winter behaviour. B. microplus was not adapted to this area whereas both H. longicornis and I. holocyclus displayed adaptation to overcome the longer and colder winter in the highlands compared with that of coastal plains. The higher altitudes must be considered as marginal areas for B. microplus. Drought during the study period made the investigations in the low altitude area unproductive.