Host Selection and Movements of Ixodes Ricinus (Acari) Larvae on Small Mammals

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Abstract
The clumped distribution of I. ricinus L. larvae in the vegetation causes a highly overdispersed distribution on small mammal hosts. This distribution pattern fits with the negative binomial distribution. Apodemus sylvaticus L. has shorter daily active time and range and hence probably picks up fewer ticks from the vegetation. In spite of this A. sylvaticus carries considerably more ticks than Clethrionomys glareolus Schreb. and Sorex araneus L. in the field. In laboratory experiments, this difference between rodents was even more pronounced. The reason for such differences in infestation is that the ticks do not accept the various host species to the same extent. Of introduced larvae, 8% in C. glareolus and 53% in A. sylvaticus succeeded in engorging. In A. sylvaticus the engorged larvae had a higher mean weight than in C. glareolus. In the fur a larger part of the ticks had more directed and faster movements towards their prediliction places on the head on A. sylvaticus than on C. glareolus. In S. araneus only a few ticks moved at all. The majority stayed on the spot where they had been placed. The behavior of the ticks on the host body explains the differences in attachment sites found in the field on different host species.