The influence of conspecific chemical cues on walking behavior of Ixodes ricinus males.

The influence of female and male cues on the male searching behavior of the sheep tick, Ixodes ricinus (Acari: Ixodidae), was studied under constant laboratory conditions by means of a computerized video tracking system. Males were released into an open glass arena in which one half had been exposed for 1 h to 5 freely walking unfed females or five males. The obtained track data were analyzed to reveal if male walking pattern was random or affected by cues of conspecifics left on the arena surface. The results showed that males spent significantly more time and walked a significantly longer distance in the area with female cues compared to the control area. Moreover, the walking path of males was more tortuous on the cues half than the control half. In contrast, walking behavior of males was not affected by male cues in any observed parameter. These results provide the first evidence that unfed females leave sex-specific semiochemicals on a substrate during their walk and that these cues have an effect on male searching behavior. Since this effect was not observed when female cues were 24-h old, the semiochemicals seem to either evaporate or are subject to degradation. The biological significance of these findings for mate-searching in I. ricinus males is discussed.