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The Seasonal and Annual Incidence of the Sheep Tick, Ixodes ricinus, in Britain
Published online by Cambridge University Press: 10 July 2009
Extract
1. Serial examinations of the degree of infestation of thirty-five flocks during a nine-year period in Argyllshire, Perthshire, Selkirk and Northumberland, showed that tick incidence is greatest in spring and decreases markedly in early summer. Evidence is given of a similar periodicity in North Wales.
2. Evidence is given of the occurrence of a slight recrudescence of activity in autumn, and of the almost complete absence of activity in winter.
3. The spring curve of activity terminated in early May in Argyllshire, in the middle of May in Perthshire, and towards the end of May in the Borders and Northumberland.
4. The estimation of the relative annual infestation, e.g., in relation to the question of spread or increase of ticks, by single annual counts is shown to be quite unreliable.
5. No evidence was obtained of an increase in density of ticks in any area during the period of observation.
6. The seasonal periodicity in activity was found to bear no relation to the density of stocking of the ground by sheep.
7. The seasonal activity of ticks in Argyllshire, Perthshire, Selkirkshire and Northumberland, was found to be related to the air temperature, expressed as the weekly average of maximum temperatures. The limits of the air-temperature range corresponding to active tick infestation are 45°F. and 60°F. (average weekly maximum).
8. The curve of tick infestation during 1937 on a moor in North-east Scotland was found to differ markedly from the normal, and the possible explanations of the discrepancy are discussed.
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