Computer-controlled olfactometer system for studying behavioral responses of ticks to carbon dioxide

An olfactometer system that consisted of a laptop computer, a carbon dioxide analyzer, and an apparatus to control gas flows was designed to study ixodid tick behavioral responses to varying carbon dioxide (CO2) concentrations. The system provided a method to regulate and measure stimulatory CO2 concentrations (1-99 ppm) above ambient CO2 background levels. Adult Amblyomma americanum (L.) and Dermacentor variabilis (Say) demonstrated behavioral responses to CO2 concentrations as low as 9 ppm above the mean ambient background. Behavior (questing, initial movement, or activity rate) of adult ticks was observed before and during CO2 stimulation. Between the species, significantly more D. variabilis quested during stimulation, whereas significantly more A. americanum moved. Questing behavior between the sexes for either species was not significantly different. Initial movement for male A. americanum was significantly greater than for females. Activity rate was greater in A. americanum than in D. variabilis and significantly greater in male D. variabilis than in females.