compound symmetry, Cronbach's alpha, internal consistency, test reliability,

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The appetence responses of the ixodid ticks Ixodes rubicundus and Rhipicephalus punctatus to various stimuli were quantified under laboratory conditions. A greater percentage of I. rubicundus generally responded to the different stimuli at lower than at higher temperatures while the converse was usually true for R. punctatus. Radiation heat and shadowing evoked a response in the greatest percentage of I. rubicundus, whereas CO2 and host odour were responsible for a similar reaction in R. punctatus. A single perturbation of the substrate caused more than 50% of I. rubicundus to respond while constant perturbation resulted in a progressive decrease in the proportion of ticks reacting. Significantly more R. punctatus than I. rubicundus were attracted to a CO2 trap and the R. punctatus were also attracted to the trap over a greater distance. Significantly more older than younger ticks of both species responded to the various stimuli.

Spatial distribution of the Karoo paralysis tick (Ixodes rubicundus) has been studied in a paralysis enzootic area of the southwestern Orange Free State. Significantly more females than males were collected from the vegetation. Most ticks (99%) used grass as questing sites at a height of approximately 45 cm (range 10-97 cm), which correlates with the size of host animals. No significant differences between the questing height of male and female ticks were evident. The ticks were found on most of the grass species present and, except for the genus Eragrostis, no specific preference was evident. When questing, the capitulum of I. rubicundus is usually (90%) directed towards the ground. Seventy-eight percent of the ticks occurred singly on a specific grassblade or flowerhead. In those cases where two ticks occurred together, no sexual aggregation was evident. Most ticks occurred under or close (mean = 62 cm) to the crown cover of specific shrub or tree species. These plant species were characterized by a dense crown cover with a mat of decaying leaf litter underneath. The preference of the tick for wild olive trees (Olea europaea africana) suggests that, except for the physical characteristics of this tree species, host factors may also be important. Significantly more ticks were distributed on the cooler, more protected southern sides of vegetation in comparison to the northern sides.

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