The Rate of Predation and Its Temperature Dependence in a Tiger Beetle, Cicindela Hybrida

The tiger beetle Cicindela hybrida and its insect prey constitute a simple predator-prey system in which the predator searches at random and the prey is continuously renewed. By means of the basic functional response equation, modified for this situation, it is shown that the rate of predation is strongly dependent on the ambient temperature. The parameters of the model were determined in the field at temperatures between 200 and 44TC. The speed of locomotion, handling time and success rate were little dependent on temperature because of the thermoregulatory abilities of the tiger beetles. The fraction of time spent searching increased to a plateau above 36TC. The number of prey items present increased to a maximum at 360C and then decreased at higher temperatures. The resultant capture rate has a bellshaped distribution in relation to temperature. It increases from less than one prey/h at 20'C to a maximum of ca. 7 prey/h at 36TC. At high temperatures the rate falls off. The number of prey captured at different temperatures was also observed directly and a good agreement was found between observed and calculated values.