Exokinetic Responses of Argas Cooleyi and Ornithodoros Concanensis (Acari: Ixodoidea: Argasidae) to Various Environmental Temperatures

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Abstract
Nymphal Argas cooleyi and Ornithodoros concanensis were tesled lo delermine their behavioral responses and physiological tolerances to the temperature extremes they would likely encounter in the physical environment of a Cliff Swallow ( Petrochelidon pyrrhonota ) nesting site. On a 15–35 °C temperature gradient, O. concanensis consistently failed to aggregrate or move into the portion of the gradient with temperatures above 27°C, and 80% of the tick occurrences noted were in the lower ½ of the temperature gradient with temperatures of 15–23 °C. Temperature choice experiments that tested the ability of ticks 10 discriminate between 2 different temperatures also indicated a tendency of O. concanensis to aggregrate on cool substrates. Groups of A. cooleyi , also tested on a 15–35 °C temperature gradient, appeared to avoid extremely high or low temperatures, or the upper and lower ends of the gradient. Apparenlly, response to an aggregrating pheromone exerted a greater influence than temperature on A. cooleyi , causing ambiguous test results. As in the case of O. concanensis , in temperature choice experiments A. cooleyi demonstrated the capability to distinguish temperature differences of 2 ± 1°C. Unlike O. concanensis, A. cooleyi tended to avoid temperatures both above and below 25 °C. In tests of thermal tolerances, both species survived 1-h exposure to 45 °C, but 100% mortality occurred al 47.5 °C. Both species also survived for 12 h at −5°C, but succumbed at a temperature of °15 °C.

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