Resource Partitioning by Ovipositing Cicadas

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Abstract
Host plant utilization patterns of the 3 cicada spp. [Magicicada septendecim, M. cassini and M. septendecula] in 65 m2 of disturbed (roadside second-growth) habitat was examined. The entire resource spectrum of available host plants was measured. Of the 22 host species, 18 were used by at least 1 cicada species (15 by all three, 2 by two, one by one). An additional 7 host species were selectively examined in an adjacent area. A total of 22,799 eggnests were counted and measured. Some hosts are preferred over others, and the cicada species agree on what they dislike but disagree somewhat on what they most prefer. Fitting the data to a Poisson distribution shows avoidance, which is adaptive because hatch can be affected by crowding. Oviposition patterns observed can best be explained by postulating that females inherit very generalized (i.e., not species-specific) criteria of preference and learn through trial and error and by watching other females; they capitalize on the finds of others. Two hypotheses may explain the totally different approaches to host utilization in mature forest versus disturbed habitats. The predator satiation hypothesis maintains that in order to satiate predators, cicadas must use a large percentage of host plants found in the habitat. Cicadas do this in mature forest by using all the dominant species, and in disturbed habitat by using a larger variety of hosts, including second-growth species. The second hypothesis is that the carrying capacity of each species is too low in the habitat of the other species to permit successful invasion and coexistence, but that disturbed habitats are suitable for all 3 spp. Edaphic and moisture conditions may prevent successful establishment of the wrong species in mature forests, but these factors may be modified in disturbed habitats.