Sussex Butterfly Conservation : Species

Butterfly Species in Sussex

Large Tortoiseshell at rest – photo by Matt Simmonds

Large Tortoiseshell

Nymphalis polychloros

Description

Until very recently Large Tortoiseshell was described as an uncommon migrant, but in 2021 that all changed when there was confirmed breeding at an undisclosed location, in East Sussex. This was the first confirmed breeding, in the county, since 1948.

Quoting from the 2023 annual report: “Large Tortoiseshell rather kept under the radar, but it had what will probably prove to be a pivotal year. It is no longer just a migrant species in Sussex. Any sighting in March or April is likely to be an over-wintering individual, and for the whole of 2023 there were around twenty records, in at least ten different localities. It seems to be gradually colonising the Sussex countryside, almost by stealth, as small colonies are so difficult to find and study. One such study involved the Ouse Valley, where Dave Harris and others searched in the spring for the presence of adults, and then a couple of months later, repeated the search for their larval webs. A total of 9 adults were found in early April. Subsequently, four webs were found in different locations, with three webs on English Elm and two webs on a Bullace. Six adults were recorded in the summer, with the first one seen on June 25th”.

During the years 2006-2024 the “average first sighting” was March 15th, ranging from February 19th to April 6th. The message is quite clear, that if you wish to find a post-hibernating Large Tortoiseshell in Sussex, the optimal time is the second half of March, and the first week of April.

A fresh specimen of a Large Tortoisehell should be a fairly straightforward ID, but this becomes a lot more difficult with very faded individuals. Leaving Scarce Tortoiseshell to one side, if we compare Large Tortoiseshell and Small Tortoiseshell there are at least six points of difference. Size: LT is slightly larger than a Peacock, whilst ST is appreciably smaller. Shape: The hindwings of LT are rather long. This means they extend/protrude, giving it a very distinctive shape. Colours of the leading edge: The colours of the leading edge are slightly subdued compared to ST, and in particular the yellow panels are a soft tawny-yellow, compared to the intense yellow of ST. Forewing markings: LT has four black spots, more-or-less equal in size. ST has just two black dots and a much larger black block. Rear edge blue lunules: LT has a short row of blue lunules that run inside the margin of the hindwings. ST has a brilliant iridescent row of blue lunules present in both forewings and hindwings. Colour of the hindwing: LT has a few brown hairs adjacent to the body, otherwise the background colour of the hindwing is orange. The inner half of the hindwing of ST is dark brown, whilst the outer half is a reddish-orange.

The eggs may be laid on a very wide variety of native trees and shrubs and these include Elm, Aspen, Poplar, Whitebeam, Sallow, Birch and wild Cherry. Fruit trees such as Pear, Cherry and Apple are also known larval foodplants.

This species is single-brooded, and in this county we might hope to see adults from mid-June to the end of July. Looking at the website dates, there are only two records after July: on 01/08/2021 and the very late date of 11/11/2023.

Where to find

As the statement above confirms, this species can be found in the Ouse Valley. There have been recent records in a number of our major woods and no doubt breeding has taken place in some of those locations. Quite understandably, precise details may not always be revealed, for fear of disturbance.