Spatial and Seasonal Patterns in the Egg Distribution of Tephritis conura (Diptera: Tephritidae)

Abstract

The distribution of the eggs by females of Tephritis conura Loew (Diptera: Tephritidae), whose larvae live endophytically in flower heads of Cirsium heterophyllum (L.) Hill (Cardueae), was analyzed. Females oviposited exclusively in young buds, where the length of developing florets was between 0.2 and 0.8 mm. Eggs of T. conura are laid in batches. Batch sizes show a highly variable but characteristic pattern. In natural populations multiple ovipositions (two or more batches per bud) commonly occur. On the basis of field data models for the spatial and seasonal distribution of the eggs on distinct resource units (flower heads) are developed. It is concluded that in natural populations of T. conura the distribution of egg batches is mainly a random process. Nevertheless, overcrowding of flower heads and food shortage for the larvae are observed only occasionally since 1) the mean egg number per individual batch does not exceed the capacity of even a small flower head, and 2) the short time period during which each bud is suitable for oviposition reduces the probability of multiple ovipositions.