A male orange tip butterfly, Anthocharis cardamines, at rest on a flower head of chives, Allium schoenoprasum. The picture shows the large compound eye of the insect, comprised of many small units known as ommatidia, and the mosaic pattern on the wings, produced by thousands of tiny scales. The "orange tip" of the common name refers to the colouring of the inner wing of males and is not seen here. The orange tip is one of the species used by phenologists to study changes in the timing of Spring events in the UK. Records show that in the years 1899-1914, the species was first observed on average on 13th May. In 1999-2014, the corresponding date was 24th April, 19 days earlier. This suggests that the species may be very sensitive to changes in the climate.