The immature stages, larval food plants and biology of Neotropical mistletoe butterflies (Lepidoptera: Pieridae). II. The Catasticta group (Pierini: Aporiina)

We present an overview of the morphology, larval food plants and general biology of the immature stages of the "Catasticta group", one of three clades of aporiine pierids that specialize predominantly on mistletoes, based on extensive field observations and captive reared material in Costa Rica, review of the literature, and examination of material preserved in museum collections. Of the 8 genera recognized in the group, 6 are restricted to the Neotropics of which detailed descriptions and/or illustrations are given for 11 species representing the genera Melete, Pereute, Leodonta and Catasticta. The life histories of these taxa are compared with those of Neophasia and Eucheira, two Nearctic genera in the Catasticta group that specialize on host trees of mistletoes. Larval food plants of the Neotropical genera include Struthanthus, Tripodanthus (Loranthaceae), Antidaphne (Santalaceae), Dendrophthora and Phoradendron (Viscaceae), all aerial-stem hemiparasites in the order Santalales. The butterflies are multivoltine and, with the exception of Melete in which adults are possibly migratory, appear to breed throughout the year. Eggs are deposited in clusters on the larval food plant, larvae feed gregariously and spin considerable quantities of silk, particularly in the late instars, adults are frequently aposematic, and at least four genera form complex mimicry rings. In Melete, Pereute, Leodonta and one species of Catasticta, larval instars III-V feed nocturnally and aggregate near the base of the host tree during the day: silken trails are constructed between mistletoe foraging sites and host tree diurnal resting sites to facilitate movement and communication. The morphology and biology of the immature stages of the Catasticta group are compared with other members of the Aporiina, particularly those of Delias, Aporia and the more distantly related Mylothris, and comments made on their systematic relationships. Simple optimization of several key life history traits in the context of a recent phylogenetic hypothesis of the Aporiina suggests aposematism (larval repellent defence and adult warning colouration) evolved once in the common ancestor of the subtribe, but egg clustering and larval gregariousness are derived traits that coincided with the evolution of mistletoe feeding. It is hypothesized that following the evolution of aposematism, the spatial distribution (patchiness) of mistletoe food plants, which are assumed to contain toxic alkaloids, has been a selective force in the evolution of larval gregariousness in these butterflies.