História natural de Paraselenis dichroa Germar, 1824(Coleoptera: Chrysomelidae: Cassidinae)

Abstract

Cassidinae Gyllenhal, 1813 is the second largest subfamily of Chrysomelidae, with about 6000 species distributed worldwide. They are extremely characteristics in terms of morphology, biology and behavior. The objective of the present work was describe the life cycle of the Paraselenis dichroa, their biological and behavioral aspects as well as identify their natural enemies and determine their effect on the immature stages. The study was conducted between February and April 2015, in the Nacional Forest of Passa Quatro (Atlantic Forest Biome), Passa Quatro, MG, Brazil. For the experiment on biology and ethology, daily observations were conducted in the morning and afternoon, evaluating 33 females and their offspring on the host plants Ipomoea sp. and Merremia macrocalyx (Convolvulaceae). In the experiment on natural enemies, there were two treatments with and without offspring protection. The species has two reproductive cycles of 2.5 months. Eggs are laid in groups on the main vein of the leaf on the abaxial face (n=25). The egg clusters are imbricated, pedunculated and the eggs are uncovered. The egg clusters presented, on average, 27.7±5.5 eggs (n=30). The average of incubation period of the eggs was 12.46±1.98 days (n=13). Larvae remain in cicloalexy during development on the leaves, except when feeding. They have the exuvio-fecal shield, on the urogomphus, as a defense mechanism. The average number of larvae that ecloded per spawn was, 14.15±11.5 individuals (n=33). The larval phase is the longest stage of the development of the immatures, lasting 24.9±3.3 days (n=20). The pupation occurs on the stem of the host plant and in this period the exuvio-fecal shield is not present. The average number of pupae was 13.4±9.9 individuals (n=23). The pupal stage duration, on average, was 9.35±2.2 days (n=14). The number of the emerged adults, on average, was 11.7±9.0 (n=16), and the total cycle time was 45.6±9.0 days (n=10). There is a clear sexual dimorphism in adults. Mothers, when manipulated, defecate and/or excrete hemolymph, as a defense mechanism. During all immature stages the females stay together with their offspring, until the first days of the newly emerged adults. There was an effect of treatments with and without offspring protection on total mortality; larval mortality; pupa mortality and survival of immatures. The natural enemy of the eggs was Emersonella pubipennis (Eulophidae). The Hemiptera Stiretrus decengutatus (Pentatomidae) was observed preying on the larvae, as well as the parasitoids of Tachinidae (Diptera), and the pupae suffered attacks by Conura sp. and Brachymeria sp. (Chalcididae). The natural history of P. dichroa is important as a starting point and basis for understanding evutionary questions and multispecies interactions.