Egg Distribution of the Southern Festoon (zerynthia Polyxena) (lepidoptera, Papilionidae)

摘要

We investigated environmental factors grouped along hierarchical spatial scales influencing the egg density of a monophagous papilionid, the southern festoon (Zerynthia polyxena) on its food-plant, the birthwort (Aristolochia clematitis). Two patch level variables were considered: habitat type (black locust plantation, clearing and hummock) and food-plant patch size. We measured several plant variables at the egg-bearing shoots. We counted the number and measured the mean height of birthworts within the microenvironment of the egg-bearing shoots. We also measured the height and counted the leaves of each egg-bearing shoot itself. Plant apparency was defined as the height difference between egg-bearing shoots and the surrounding ones. Two variables were measured on the egg-bearing shoots (hence at food-plant scale): number of leaves and position of eggs on the leaf-storeys. Habitat type affected the distribution of eggs; black locust plantations and hummocks were preferred against clearings. At a smaller scale, neither shoot density, nor food-plant apparency affected egg distribution. At the plant level, the number of eggs increased with the number of leaves, and the position of eggs also co-varied with egg density, having fewer eggs in clusters positioned higher on shoots. We conclude that spatially correlated data on butterfly egg distribution should be analysed considering the intrinsically hierarchical structure of environmental factors