Effect of host age on the oviposition and performance of Ascia monuste Godart (Lepidoptera: Pieridae)

Abstract

Neotropical Entomology 34(2): 169-175 (2005) Efeitos da Idade do Hospedeiro na Oviposição e Performance de Ascia monuste Godart (Lepidoptera: Pieridae)RESUMO -Ascia monuste Godart, conhecida como a lagarta-da-couve, é especialista em Brassicaceae e representa um dos principais herbívoros dessa família na região neotropical. O objetivo do presente estudo foi determinar a performance e a preferência de oviposição de A. monuste por folhas de couve Brassica oleracea (Brassicaceae, var. acephala) de diferentes idades. Os parâmetros utilizados para medir a performance foram tempo para pupação e para emergência, porcentagem de emergência, índices digestórios, taxas de consumo e crescimento relativos, número de ovos por fêmea, porcentagem de eclosão e peso dos imagos. Análises químicas e físicas de folhas jovens e velhas de couve foram feitas. Em geral, imaturos que se alimentam de folhas jovens exibem melhor performance que aqueles que se alimentaram de folhas velhas. Entretanto, não houve diferença no número de ovos por fêmea, indicando mecanismos de compensação, uma vez que folhas velhas possuem menor quantidade de nitrogênio e maior dureza. Fêmeas de A. monuste preferem ovipositar em folhas jovens.PALAVRAS-CHAVE: Insecta, preferência de oviposição, idade da folha, comportamento alimentar ABSTRACT -Ascia monuste Godart, known as the kale caterpillar, has a specialized diet on Brassicaceae and represents one of the main herbivores of this family in the Neotropical region. The objective of the present study was to determine the performance and oviposition preference of A. monuste for common kale Brassica oleracea (Brassicaceae, var. acephala) of different ages. The parameters used to assess performance were time to pupation and emergence, emergence rate, digestive indices, relative consumption and growth rates, number of eggs per female, hatching rate, and weight of the imagoes. Chemical and physical properties of young and old kale leaves were determined. In general, caterpillars feeding on new leaves showed better performance than those feeding on old leaves. However, no significant difference in the number of eggs per female was observed, indicating a strategy of compensation, as old leaves contain a lower amount of nitrogen and are harder than young leaves. A. monuste females prefer to lay eggs on young leaves.

How feeding on young and old leaves affects the performance of Ascia monuste orseis (Godart) (Lepidoptera, Pieridae)

“…As the results of this study show, higher amounts of nitrogen and water and less hardness of the young leaves did not significantly affect survival of the immature insects or the accumulation of biomass in the adult, as they did not affect the number of eggs laid by each female according to previous studies (Bittencourt-Rodrigues & Zucoloto 2005). However, Table I Nitrogen is an important nutrient for initial instars because it is a fundamental component for proteins composition and, consequently, for the larvae growth (Scriber 1982).…”

“…That compensation is frequently observed when there is equivalence in the fecundity (same number of eggs by female) and mortality rates, which are similar in the species under study (Bittencourt-Rodrigues & Zucoloto 2005). In that case, such physiological compensation can be verified by the similarity of efficiency in the conversion of the digested food.…”

“…That lenghtened time of development, however, indirectly affects survivorship since it increases vulnerability to predators, desiccation and the action of pathogens (Haggstrom & Larsson 1995). In addition, the hardness of the old leaves can also impair the young catterpillars mastication since their mandibular apparatus is very delicate (Gaston et al 1991, Dodds et al 1996, Bittencourt-Rodrigues & Zucoloto 2005.…”

“…acephala) Latreille 1819, the typical host of A. monuste orseis, present higher water and nitrogen content and are less hard than the older leaves (Bittencourt-Rodrigues & Zucoloto, 2005), changes which are common during the leaf development (Mattson 1980, Scriber & Slansky 1981, Slansky & Wheeler 1992. Due to these factors, some herbivorous insects grow more, survive in higher numbers, and increase their weight when they eat the younger leaves (Schewitzer 1979, Dodds et al 1996.…”

“…Due to these factors, some herbivorous insects grow more, survive in higher numbers, and increase their weight when they eat the younger leaves (Schewitzer 1979, Dodds et al 1996. In the species under study, the immature insects, when fed exclusively on young leaves, develop in a shorter period, however they obtain the same gain in mass and the same fecundity as the individuals which feed on old leaves, showing skills in food compensation (Bittencourt-Rodrigues & Zucoloto, 2005). One ought to know whether this movement to different parts of the host also causes a different performance.…”