Phenotypic variation in male Calopteryx splendens damselflies: The role of wing pigmentation and body size in thermoregulation

For an ectothermic insect, its color and size are important determinants of body temperature: dark colors absorb heat more efficiently, while larger bodies require more heat to reach a certain temperature. These dark colors are expressed using melanin, which has been intimately linked with an insect’s thermoregulatory capabilities. Melanin is also linked with immune defense and is often used as a secondary sexual character in insects. There is a potential trade-off situation between thermoregulatory capabilities, immune defence and secondary sexual characters, all of which use melanin. Some Calopteryx damselflies, such as Calopteryx splendens, have melanin-based wing pigmentation that is sexually selected and drives intra- and interspecific territorial aggressions. Our goal was to experimentally study how the wing pigmentation and body size of C. splendens males affect their thermoregulation and especially their ability to become active after being cooled down. Our results are in line w...