Specificity of communication channels in four limacodid moths: Darna bradleyi, Darna trima, Setothosea asigna, and Setora nitens (Lepidoptera: Limacodidae)

Abstract

Darna bradleyi Holloway, D. trima Moore, Setothosea asigna van Eecke and Setora nitens Walker are sympatric and coseasonal limacodid moths in plantations of oil palm, Elaeis guineensis Jacq. (Arecales: Palmae), in Borneo, southeast Asia. We tested the hypothesis that these four species maintain reproductive isolation through specificity in diel periods of communication, microlocation for communication and/or communication signal (pheromone). Studying diel periodicity of calling behavior by female moths and response by male moths to traps baited with virgin females or synthetic pheromone, we determined that sexual communication of D. bradleyi and D. trima took place from ˜17:30 to 18:45 hr and that of S. asigna and S. nitens from ˜18:45 to 20:00 hr and from ˜18:30 to 19:30 hr, respectively. Over 80% of male S. asigna and S. nitens were captured in pheromone-baited traps suspended >5 m high, whereas male D. bradleyi and D. trima were captured mostly in traps <5 m high. Synthetic pheromone baits attracted male moths in a species-specific manner. Moreover, baits containing both S. asigna and S. nitens pheromones failed to attract any male moths, indicating that female S. asigna and S. nitens, with overlapping communication periods, use bifunctional pheromone components that attract conspecific males while repelling heterospecifics. Similarly, addition of D. bradleyi pheromone to S. asigna or S. nitens pheromone reduced attraction of male S. asigna and S. nitens. The failure of D. bradleyi and D. trima, which overlap in time and microlocation for communication, to evolve bifunctional pheromones may be attributed to the recent occurrence of sympatry between D. bradleyi and D. trima in Borneo, apparently too recent for bifunctional pheromones to have evolved. We conclude that D. bradleyi, D. trima, S. asigna and S. nitens utilize any or all of diel periodicity, intra and interspecific effects of communication signal and/or microlocation for signaling, allowing these limacodids to co-inhabit the same habitat and remain reproductively isolated.