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University of Sussex rallies to rescue rare butterfly

© Gilles San Martin

© Peter Eeles

A Life Sciences technician at the University of Sussex led efforts to successfully save the eggs of an elusive butterfly species before a disease-stricken Elm tree was felled on campus.

Crispin Holloway worked with a team of volunteers and experts from the Sussex Branch of Butterfly Conservation and Brighton and Hove arborist, Alister Peters to search for and save the eggs of the White-letter Hairstreak from branches as they were cut and removed.

The eggs found (which look like miniature 1950s UFOs) will be kept so the caterpillars can be reared in captivity or transferred to a healthy Elm tree elsewhere on campus, helping to save the local population of this rare butterfly.

Although rearing the species in captivity is difficult, it would provide the eggs with protection from predators and allow researchers a rare chance to monitor the early stages of the butterfly’s life cycle.

Crispin Holloway, who is a volunteer for the UK charity Butterfly Conservation and runs butterfly surveys on campus, said: “This rescue project was a valuable exercise to confirm if the butterflies are breeding on campus grounds and gives us even more reason to look after the existing Elm trees and the butterfly population.

“The planting of disease-resistant Elm trees on campus will be important but it may take several years before these are mature enough to produce blooms and seed which the caterpillars of the butterfly will prefer to feed on.

“Future butterfly and egg surveys on the university grounds will help us learn more about this butterfly and how to help it.”  

The White-letter Hairstreak can be identified by the distinctive ‘W’ marking on the underside of its wing and its caterpillars feed solely on Elm.

In the 1970s, the butterfly’s population declined dramatically due to Dutch Elm disease killing off huge numbers of our native Elm trees.

Since then, the White-letter Hairstreak’s population has dipped by 93% across the UK and, in the south east, the butterfly has declined in its distribution by 29% since the mid-1990s.

Butterfly Conservation’s Regional Conservation Manager for the south east of England, Steve Wheatley, said: “This is one of only five Hairstreak species in the UK and it is very rarely seen.

“It relies entirely on Elm, so every tree lost to disease is a potential blow, which is why it's so fantastic that the University of Sussex are doing what they can to help this important butterfly.”

The butterfly is now a UK Biodiversity Action Plan Priority Species.

Crispin believes the University of Sussex campus is unique as a habitat due to the number of mature, native and healthy Elm trees in a National Park and Biosphere.

Crispin explained: “The University is incredibly lucky to have so many healthy and mature Elm trees.

“In the wider Brighton and Hove region, we’re also lucky to have the largest stock of Elm species in Britain, largely thanks to the control measures implemented by the Brighton and Hove City Council and the East Sussex County Council. These measures were designed to limit the growth of the Elm Bark Beetle population, which carries the fungal infection.

“As a result, there are now approximately 17,000 Elm trees in Brighton and Hove.”

Ashley Wilcox, Sussex Estates and Facilities Grounds Manager, agreed to ensure that the work of tree surgeons would be slowed to allow time for volunteers led by Crispin to search for eggs.

Crispin added: “Monitoring butterflies gives us a very good idea of a site’s ecological health and can help us to identify how suitable land management could enhance the ecology, linking the habitats and ecosystems of the campus with the surrounding South Downs National Park, as well as the Brighton and Lewes UNESCO World Biosphere Region."

After the removal of the 10.5 metre tree, estimated to be somewhere between 110 and 124 years old, the bark and branches were burnt at a site away from any other Elms to lessen the likelihood of the fungus being transferred to them.

However, part of the Elm has been preserved on the campus at Falmer so that social insects - such as ants, bees, termites and wasps - and birds can live in it. The trunk will also be used by Sussex students for nature study and scientific inquiry.  

By: Stephanie Allen
Last updated: Wednesday, 13 February 2019