The status of the Green-veined White does not appear to have undergone any significant changes in the county since the earliest published records in the mid-1800s. Over the last twenty years data has revealed that it is the most widespread butterfly in Cheshire with sightings in 98% of recorded tetrads (2km x 2km squares).
Whilst this insect is found throughout the county it is along the low-lying river valleys of the Dee , Gowy, Weaver and Mersey that the greatest concentrations occur. It also seems likely that data from the Cheshire Butterfly Recording Scheme may even be under-representing this species as a few contributors simply split all their sightings of “white” butterflies between the Large White (Pieris brassicae) and Small White (P. rapae). In many areas all three of these insects occur together, but in the hillier Pennine regions in the east of the county sightings of the Green-veined White greatly outnumber the other “whites”. The one area where the Large White and Small White are normally seen in larger numbers (much to the annoyance of some gardeners) is around vegetable plots where they breed on cultivated brassicas, causing considerable damage. On the other hand, the Green-veined White is not a pest of cabbage crops, but has a preference for breeding in the countryside, especially on Garlic Mustard (Alliaria petiolata) or Cuckooflower (Cardamine pratensis). These plants are most abundant in damp areas, along hedgerows, ditches, woodland rides or on moorlands. Despite having a rather weak fluttering flight this petite and attractive butterfly is a mobile insect, at least on a relatively local scale. It does not live in colonies, but often roams around in search of suitable nectar sources or foodplants.
Unlike the Large White and Small White the numbers of the Green-veined White are seldom augmented by migrants with the result that it does not normally show significant changes in abundance from one year to another. Any changes which do occur are probably more closely associated with climatic conditions, with this being especially noticeable after a year of high summer temperatures when breeding conditions do not favour this insect. Records show that in the following year numbers can fall considerably, although there is evidence that populations quickly recover from these setbacks.
The Green-veined White can be seen throughout the year as it has two overlapping broods with regular sightings from late April to mid-September. In Cheshire there is little evidence of a third brood in the autumn. Peak numbers of the first emergence occur in late May, with the second brood normally being more numerous and peaking in late July or early August. Dates of extreme sightings in Cheshire are 13th March 2003 in Holmes Chapel and 1st November 2009 at Rixton Claypits.
Written by Barry Shaw for News, the Cheshire and Peak District Branch of Butterfly Conservation magazine.