Host availability hypothesis: Complex interactions with abiotic factors and predators may best explain population densities of cicada species

Advertisement calls of some cicadas are so loud that they are a nuisance to city-dwellers in Korea. We hypothesized that the densities of cicada species were directly correlated with the availability of host plant species. We conducted complete enumeration surveys of exuviae in Hyalessa fuscata, Cryptotympana atrata, Meimuna spp., and Graptopsaltria nigrofuscata in three representative habitats in Republic of Korea: metropolitan, suburban, and country. We measured resource-weighted density of each species based on the area and the number of trees, and used those values to calculate organism-weighted density, which measures the intensity of competition that an individual experiences sharing its host with others of its own species. H. fuscata was the dominant species in all three habitats. H. fuscata and C. atrata comprised a minimum of 75.2% of all cicadas across all habitats and sampling periods. Resource-weighted densities of H. fuscata and C. atrata were much higher in the metropolitan habitat than in the country habitat. Habitat was a significant factor for variations in organism-weighted densities in C. atrata and G. nigrofuscata, but it was not in Meimuna spp. and H. fuscata. Some of the results concerning the percentages of trees without exuviae and preferred plants seemed to support the host availability hypothesis in C. atrata, Meimuna spp. and G. nigrofuscata, but they may not in H. fuscata. The similarity between resource-weighted and organism-weighted densities suggests that factors other than host availability, speculatively abiotic factors and predators, may also account for the patterns of population densities in C. atrata and G. nigrofuscata.