The effect of spring temperature on the appearance dates of British butterflies 1883-1993

This paper examines the first appearance of butterflies using two sources; historical data from the former phenological reports of the Royal Meteorological Society and recent data from the extant Butterfly Monitoring Scheme. Using regression techniques mean dates of appearance are related to Manley's central England temperatures and are then examined for other, unexplained, trends over time. The observed relationships suggest that, in the absence of evolutionary change, climate warming of the order of 3 degrees C could advance butterfly appearance by two to three weeks. The flowering of two of the larval foodplants of the orange tip butterfly is also examined, with the conclusion that synchrony is likely to be maintained by a similar advance in timing. The consequences of such changes to the phenology of British butterflies are discussed.