As Earth's climate changes, many butterfly species are emerging — from cocoons or from hiding — earlier in spring. Researchers have identified traits in UK butterflies that predict the largest shifts seen in emergence times over the past 30 years.
Sarah Diamond, then at the University of North Carolina, Chapel Hill, and her colleagues analysed a data set on UK butterflies such as the speckled wood (Pararge aegeria, pictured) during a period in which the country's spring temperatures rose by 1.5 °C. Butterflies that eat a lower diversity of plant species as caterpillars showed larger shifts in emergence time. The authors suggest that the butterflies may be tracking changes in their host plants' annual schedules.
Bigger shifts were also apparent in butterflies that overwinter as adults rather than as pupae or larvae. These species may respond more quickly to warm temperatures, the authors say.
R. COOPER/NATURE PICTURE LIBRARY