Biologia e ecologia de Pleuroptya silicalis (Lepidoptera: Crambidae) e Urbanus esmeraldus (Lepidoptera: Hesperiidae): taticas defensivas e interações com formigas em arbustos de Urera baccifera (Urticaceae) / Biology and ecology of Pleuroptya silicalis (Lepidoptera: Crambidae) and Urbanus esmeraldus (Lepidoptera: Hesperiidae): defence tactics and interactions with ants on shrubs of Urera baccifera (Urticaceae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

1. This work investigates the biology and behaviour of two lepidopteran species that feed on the nettle Urera baccifera (Urticaceae). The plant is visited by 22 ant species, which are attracted by the nettle s fleshy fruits and pearl bodies. Larvae of both species build leaf shelters: Pleuroptya silicalis (Crambidae: Pyraustinae) makes leaf rolls, and Urbanus esmeraldus (Hesperiidae: Pyrginae) builds two different kinds of shelters (peaked-roof shelters and leaf folds). Both species have 5 instars of development and present morphological and behavioural similarities to other members in each of their families. 2. Larvae of P. silicalis fill the leaf rolls with silk and faeces (frass). Artificial rolls, very similar in shape and size, but without silk or frass, did not prevent termite workers glued on the inside from being preyed by ants. Although frass did not alter the behaviour of ant foragers in the laboratory, faecal pellets could play an important role against predators and parasitoids by mechanically preventing them from entering the roll. 3. Larvae of Urbanus esmeraldus throw their faecal pellets at great distances. We experimentally demonstrated that frass located near the base of an artificial shrub induce foraging ants to climb on the plant in greater numbers than faecal pellets 30 cm away from the plant. Thus frass ejection influences directly larval vulnerability to ants. 4. Fifth-instar larvae of U. esmeraldus cut the petiole of the leaves they rest and feed. Ants, however, are not deterred by the cut petiole and it is suggested that this larval behaviour could be related with avian predation pressure. Because the cut leaves soon wither, the visual effect can be deceptive for insectivorous birds that tend to forage more often on healthy leaves. Alternatively, cutting the leaf could reduce the plant?s secondary compounds, or decrease attack by parasitoids that use leafborne vibrations to locate their hosts. 5. In 2006 ant presence did not affect infestation by lepidopteran larvae on U.baccifera shrubs. Although ants have been reported by other authors to decrease caterpillar infestation in previous years, at increased herbivore abundance ant visitation may not be sufficient to suppress caterpillars on hostplants.

ASSUNTO(S)

estrategias defensivas urbanus behavior pleuroptya silicalis lagarta do sombreiro formigas - comportamento urera baccifera defence strategies ants

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