These two butterflies are primarily white with black markings and generally can be distinguished by size, as the names imply. However, occasionally there can be “below average sized Large Whites” and “above average size Small Whites”, hence giving the phenomenon of there being small Large Whites and large Small Whites! There is only one reliable way to differentiate between the two species and that is in the extent of the black marking at the tip of the forewing. In the Large White this extends well down the outer edge of the forewing while in the Small White the black mark is restricted to the wing tip.

They are generally regarded as unwelcome visitors to a cabbage patch as unfortunately we grow their caterpillar foodplants in abundance. The Large White lays its eggs in batches and they live gregariously whereas the Small white lays its eggs singly. The caterpillars are very different with the Large White being black with yellow markings and the Small White a well camouflaged green colour. As well as cultivated brassicas both species also use nasturtium and wild cruciferous plants. At least doubled brooded, sometimes three. Main flight periods late March to June and late July to September. Both species overwinter as pupae.

Occasionally our resident breeding populations are augmented by inward migration.