Large White

Pieris brassicae

General Distribution and Status

This species can be seen almost anywhere in the whole of the British Isles. Before the 1950s it was very abundant but the increased use of pesticides on agricultural crops caused significant falls in its numbers. However, it is still very common and a number of immigrants from mainland Europe supplement breeding populations here. According to the UK Butterfly Monitoring Scheme numbers have dropped by about a third since 1976 (Brereton et al.). The situation in Hertfordshire and Middlesex is similar although in the last ten years abundance has significantly grown despite poor seasons in 2016 and 2017 (Wood, 2017, 2018). Numbers were also well down in 2021 compared to 2020 (Wood, 2022). Apart from pesticides as noted above, other factors like larval predation and parasitism have a huge effect on Large White populations.

UK distribution map
UKBMS Species summary (2020)

Habitat Requirements

The Large White occurs in almost every habitat type like gardens, allotments, and farmland.

Larval Foodplants

Cabbages Brassica spp.. The brassica noted by Sawford include Brussels Sprout, Kale, Broccoli and Oil-seed Rape. He also mentions Nasturtium Tropaeolum majus and Wild Mignonette Reseda lutea.

Adult Food Sources

Buddleia Buddleja davidii (1074), Lavender Lavandula x intermedia (175), Red Valerian Centranthus ruber (85), Runner Bean Phaseolus coccineus (68), Honesty Lunaria annua (65).

Historical Records

It seems that the Large White has always been very common in Hertfordshire. For instance, Foster in 1934 states it as 'generally abundant'. Some years provide very high populations as in 1959 when reports of third brood specimens were found (Bell) and in 1979 (Waterton).

Local Distribution and Abundance

The Large White is present in every tetrad as indicated on the map. The larger parks in the district namely, Fairlands Valley Park, Knebworth Park and Great Ashby Park, attract the highest populations. Ken King counted 73 specimens on 24 July 2004 in his Knebworth Park transect and I estimated at least 50 at Norton Green on 1 August 2013. 2018 was an excellent year with numbers hitting peaks before the middle of July in a few places. 55 individuals were counted on 9 July on my Knebworth Park transect. 2021 received the highest number of reports during the survey with a total of 264 from which a large majority was submitted to the Big Butterfly Count scheme during the peak of the butterfly's flight season. The flight season appears to have started earlier in 2022 with 15 reported from St Mary's churchyard in Aston on 15 June. In 2023, slightly fewer speciemens were reported than in 2022 and the decline was more apparent after July.

Transect weekly counts

Stevenage (South Fairlands Valley Park) transect 1993-2023

The heatwave in July 2013 probably contributed to the highest annual count of 131 in that year although a large proportion of these were likely to be migrants. After a poor couple of years in 2016 and 2017 numbers picked up enormously in 2018 aided by the hot and dry weather in June and July, and immigration from the Continent. However, there was not a significant increase in similar weather in 2022. Very few individuals made an appearance (4) in 2023 - the joint worst year.

Knebworth Park transect 1996-2010 and 2017-2023

The species showed a slight positive trend in the latter half of the 2000s but with no records between 2011 and 2016 no current trend can be determined. 10 were seen here in 2019, the worst year during the survey despite some fine weather in the summer like in 2018 when over 100 were recorded.

Knebworth Woods transect 2017-2023

A good season in 2018 with about half the specimens found by the footpath between The Firs and Newton Wood. As abundance was also high in the other two transects most specimens were likely to be immigrants.

Pryor's Wood transect 2000-2022

Populations of this species have fallen in this decade which does not align what is occurring elsewhere in Hertfordshire. Perhaps a lack of nectar sources or breeding habitat is a cause. 53 individuals were recorded in 2002, the best weekly count being 26 on 26 July.

Life History

Earliest date: 1 April 2004 at Knebworth Park
Latest date: 18 October 1997 at Benington Lordship

The Large White overwinters as a pupa so if there is warm weather in March as in 2004 facilitating speedier development then emergence of the adults should start in early April. As indicated on the chart, the second brood is usually much larger with a peak in late July. The second generation is augmented by migrants from the Continent. Any individuals seen in October may be of the third generation especially if warm weather prevails in late summer and September as was the case in 1997. Large batches of eggs are laid mainly beneath the leaves of Brassica plants. The gregarious larvae can be attacked by the parasitic larvae of the wasp Apanteles glomeratus which provides some control over the populations of the butterfly. Pupae are usually found on walls and tree trunks.
More details on the UK Butterflies website

Behaviour/Observation notes

The Large White is very active so it can be difficult to take close-up pictures of one. In addition, the wings are often closed when feeding on flowers so the best opportunity for taking photographs is very early in the morning when they are often lethargic and their wings are more likely to open (Riley). Usually, the butterfly's size distinguishes it from the other 'whites' but very occasionally, the Large White is on the small side and could be confused with a Small White. The larger and darker tips of the forewings identifies it as a Large White.

Variations/Aberrations

There are many variations and aberrations but are rare apart from minor ones like smaller size.
Find out more on the UK Butterflies website