An Analysis of Stimuli Used During the Courtship of the Monarch Butterfly, Danaus Plexippus
MetadataShow full item record
Monarch butterflies overwinter in certain areas of Southern California, forming massive colonies. Within these colonies mass mating has been observed. Most of the mating activity occurs during the last two weeks in February. Males actively pursue females in a fast and erratic mating flight. During this aerial phase the male lands on top of the female forcing her to drop or spiral to the ground. The male then probes her with his abdomen in an attempt to copulate as the female appears to resist his attempts. After a pair successfully copulates, the female becomes passive while the male carries her to the treetops where insemination occurs. The courtship consists of responses to a complex series of external stimuli. These stimuli include visual, chemical and tactile cues. This study investigated both chemical and visual cues involved in the attraction of the male to the female during the mass mating observed in February. One hypothesis is that the female emits an odor or pheromone which initially causes the male to pursue any moving object. The male is reinforced in his behavior by further chemical and tactile cues, as he pursues her avidly and finally comes in physical contact with her. This hypothesis is supported by data which demonstrates that males selectively pursue females over males during their mating flights. An opposing hypothesis claims that rather than the chemical stimulation, the male is first attracted to moving objects, followed by further visual stimulation as he perceives a change in the female's flight pattern. This causes the male to avidly pursue the female. Upon physical contact his behavior is again reinforced and the courtship proceeds. This hypothesis is supported by data which demonstrate that females are pursued differentially based on certain changes which may cause the noted difference in the female's flight pattern. A third conclusion is that the physiological changes which are due to how much each butterfly is disturbed before it is tested seem to be the most important factor in dictating the butterfly's behavior.