Populations of wetsalts tiger beetles, Cicindelidia haemorrhagica, within Yellowstone National Park (YNP) actively hunt directly on hot surfaces associated with active thermal springs. In YNP, C. haemorrhagica is only found associated with hot springs. However, as opposed to C. haemorrhagica outside YNP and other warm-adapted tiger beetles, the YNP beetles do not seem to exhibit typical behavioral thermoregulation to lower their body temperatures. Therefore, to better understand this phenomenon, we sampled three populations of C. haemorrhagica, from two locations within YNP and one non-hot springs location near Mountain Home, Idaho. We measured internal body temperatures of collected beetles by inserting thermocouples lengthwise into their abdomens. Beetles were suspended 2mm over a heated water bath at 40-55 ˚C by 5 ˚C increments. This temperature range is typical of surface temperatures where the YNP beetles rest and hunt. Internal temperatures of YNP beetles were directly compared to the Idaho beetles through paired treatments. Results show strong statistical evidence of differences in internal body temperatures between the YNP and Idaho beetles. YNP beetles had lower internal body temperatures than Idaho beetles by an average of 1.1 ˚C among the four temperatures tested. Our findings suggest that there is likely a physical or physiological mechanism that is responsible for the lower internal body temperature.
.jpg "Robert K.D Peterson photo")