Time series analysis of Holly Blue records in Yorkshire - uncovering a parasitoid

摘要

The recorded numbers of the butterfly Holly Blue Celastrina argiolus have been shown to cycle up and down every 4-6 years and this has been attributed to the caterpillar population being parasitised by the larvae of the ichneumon Listrodomus nycthemerus (Revels, 1994, 2006). Revels provided convincing evidence of the host-parasitoid relationship between the butterfly Holly Blue and the parasitic ichneumon L nycthemerus by collecting Holly Blue caterpillars and rearing them through to chrysalis. Overa period of 15 years he showed that the proportion of chrysalises that produced either Holly Blue butterflies or L. nycthemerus fluctuated; at the peak of the cycle almost all chrysalises hatched into a Holly Blue adult butterfly and at the trough of thecycle almost all chrysalises (99%) produced an adult L. nycthemerus. The cycle from peak to trough took 4-6 years to repeat with parasitic wasp numbers lagging behind butterfly numbers by one or two generations. Though Holly Blue young caterpillars areattacked by the tiny braconid wasp Cotesia inducta it is L nycthemerus which appears to largely drive the cycle.