Investigations on the host seeking and finding ofArgas (Persicargas) walkerae (Ixodoidea: Argasidae)

Abstract

In investigations concerning the influence of stimuli emitted by chickens on the host-finding behaviour of hungry female adultArgas walkerae ticks, we found that 92.5% of the ticks migrated to the stimulus source following their simultaneous exposure to odours and to a CO₂ gradient increasing in the direction of the chicken, as opposed to 67.5% following their exposure to kairomones of chickens in the absence of CO₂. Migration of the ticks toward the stimulus source was precipitated by a wide range of CO₂ concentrations (varying from 0.06 to 1 vol% within the odour mixture) but always required an increasing CO₂ gradient in the direction of the chicken, whereby differences in concentration of 0.01 vol% over a distance of 2.5 cm were sufficient. During exclusive confrontation with either CO₂ or heat in a gradient otherwise analogous to that emitted by a chicken, only 27.5% and 55% of the female ticks migrated to the stimulus source, respectively. Accordingly, odours emitted by chickens are considered to represent an essential stimulus modality, whereas body heat and CO₂ are regarded merely as secondary, non-specific stimulatory agents. Investigations involving the exposure of ticks to a habitat similar to a chicken roost revealed that host seeking and finding are not influenced by gravity and occur only in darkness and that the portion of host-finding ticks diminishes with increasing distance from the blood donor.