Biologia, comportamento e inimigos naturais de Omaspides pallidipennis Boheman, 1854 (Chrysomelidae: Cassidinae)

Abstract

The chrysomelids exhibit great diversity of natural enemies and wide variety of defensive strategies against these. Among the different defensive adaptations of the subfamily, it highlights the subsociality as it is a rare phenomenon in Chrysomelidae. In this research it was studied the subsocial specie Omaspides pallidipennis Boheman, 1854 (Chrysomelidae: Cassidinae), with the main objective to observe the subsociality, and describe, also, their life cycle and its interactions with natural enemies and with the host plant. The observations and experiments were conducted in a natural environment (Atlantic Forest). It were recorded the timetables of oviposition, outbreak and emergency in order to know the time of development of immature. Females were experimentally removed from their egg-clutches to test the efficiency of maternal care. They were also exchanged with other offspring for the verification of altruistc behavior. Natural enemies and the visitors of extrafloral nectaries were collected in order to check if there was a relationship between predators and visitors. Field experiments showed that O. pallidipennis is a monophagous specie, feeding only I. alba (Convolvulaceae). The female remains close to immature throughout the period of development of these, feeding only when the larvae do. The larvae, in the first two stages, feed between the veins, scraping the leaf surface. From the third stage they feed, also, the veins and petioles. Except when they feed, they remain always in cicloalexy. The subsociality proved to be essential for the survival of offspring. All the offspring experimentally tested were predated. The females that were exchanged remained on the offspring that were not theirs however they did not remain on the offspring of another species. It is speculated that this altruism is due to a possible selection of kin selection, however, phylogenetic analyzes should be performed to confirm this hypothesis. The natural enemies are of various taxa: Lepidoptera, Nematoda, Diptera, Hymenoptera, and Coleoptera. Predatory species belonging to the last two orders were found, also, in extrafloral nectaries of the host plant. The Eulophidae (Hymenoptera) were the greatest enemies during the stage of egg. This research shows the importance of the work conducted in the field for the comprehension and understanding of biology and the interaction between organisms.