Fall 2007

Many insects rely on thermoregulation to maintain body temperatures independent of the surrounding environment. Basking is one of the most efficient ectothermic tactics. Several studies have examined the effects of temperature on larval growth and development, melanic coloration, and behavioral characteristics. However, thermoregulation during molting has been less well studied. Based on evidence from previous studies done on thermal behavior, I hypothesized that monarch caterpillars would thermoregulate during the molting process in a manner different to thermoregulatory patterns observed during feeding. This study also assessed whether or not caterpillars are behaviorally restrained from thermoregulating while molting. To address the issue, an observational study of monarch butterflies was performed at Pinjarra Hills in Brisbane, Australia. Under natural conditions, monarch larvae were monitored on milkweed plants over several days both during a hot time (November 2006) and a cooler time (May 2007) of year. For each located instar, body temperature was recorded along with ambient temperatures from the surrounding environment, such as leaf surfaces in the sun and shade, the stem, bud, and ground. The stage of each instar, location within the sun or shade, and other behavioral activities were recorded as well. Full statistical analysis was not performed, althoug