Insects of Western North America 11. Bioluminescent behavior of North American firefly larvae (Coleoptera: Lampyridae) with a discussion of function and evolution
Buschman, Lawrent L., author
C.P. Gillette Museum of Arthropod Diversity, publisher
Observations were made on the ecology, natural history, and glowing behavior of five North American species of firefly larvae, two Pyractomena LeConte, two Photuris LeConte, and one Photinus Laporte. These observations focused on response and periodic glowing. Response glows were long-lasting glows produced by resting/hiding larva in response to a threatening stimulus. Periodic glows were short spontaneous glows produced by actively crawling larva. Durations of three short periodic glowers averaged 0.8 to 3.5 seconds with a duty cycle of 30 to 46%. Durations of five long periodic glowers averaged 4.1 to 6.5 seconds with a duty cycle of 40-52%. Larvae started glowing ca. 1 hr. after sunset and glowed all night until about 20 minutes before sunrise. Some 72-87% of periodic glows were produced during locomotion. Glowing and locomotion were significantly affected by time in the laboratory and by feeding status. Larvae seemed to switch between response and periodic glowing as though these were two alternative physiological conditions. When firefly larvae were crawling and glowing periodically, the first defensive response to disturbance was to freeze and stop glowing periodically. When similar larvae were hiding the first response to disturbance was to glow responsively. Response glowing appears to be part of a package of defensive behaviors that includes: nocturnal activity, camouflage, freezing or fleeing, response glowing, and emitting defense chemicals. Periodic glowing appears to be part of a second package of defensive behaviors that includes: nocturnal activity, camouflage, stopping periodic glowing, and freezing or fleeing. Glowing of firefly larvae did not seem to be involved in prey capture or feeding. The interaction between larvae and ants was unexpectedly non-hostile, as though larvae had chemicals to pacify ants. Vertebrate predators were probably the driving force in the evolution of aposematic defenses. No evidence was found to support any of the non-defensive functions for bioluminescence in firefly larvae. The function of bioluminescence in firefly larvae can best be understood in the context of the evolution of bioluminescence. The forces that may have driven the evolution of bioluminescence may still be active in modern firefly larvae.
March 10, 2019.