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Iar Wen Wythiennog
Green-veined White
(Artogeia napi)

Abundant throughout the area, this is one of our commonest butterflies, which survives even in agricultural districts, provided some areas of unimproved, wet land remain. The species extends into the hills to at least 500m and probably higher and is one of the few species to do so.
The Green-veined White is a bivoltine species with a mid-summer gap between generations. However, due to a disparity in emergence times between the lowlands and uplands, even on those days when there are no butterflies at sea level there may still be some flying in the mountains and vice versa. Thus there is no single day between April and September (inclusive) when an adult butterfly cannot be seen somewhere in North Wales. An interesting question relates to the relative sizes of the two generations. Recent transect data suggests that, in North Wales, the spring brood is the larger of the two which contrasts with the situation further south in Britain.

The larvae utilise the same foodplants as the Orange-tip but feed on the leaves rather than the flowers and fruits and are thus more tolerant of human interference. The caterpillar feeds on Lady's Smock or Cuckoo Flower (Cardamine pratensis) and Garlic Mustard or jack-by the Hedge. For example if cattle are turned out onto a field with flowering Cuckoo-flower the Orange-tip ova and larvae may all be destroyed while the Green-veined Whites survive. Similarly, when the local authority mows a roadside verge at an inappropriate time of year, the Green-veined Whites stand a better chance of survival.

At a distance the 'whites' can be hard to differentiate. However, the dark-greenish markings along the veins on the underside of the wings of this butterfly are usually easy to see if a close view is obtained.