“There is no blue without yellow and without orange” A reintroduction success story.

Photo courtesy of the National Trust

Photo courtesy of the National Trust

When Van Gogh wrote this to Emile Bernard, he was actually referring to colour. However, switch one the latter colours to red and he could easily have been talking about the Large Blue butterfly (Maculineas arion). For there would be no Large blue without red ants (Myrmica sabuleti) and this unfortunately became reality in 1979 after the Large blue was declared extinct. Hard work has thankfully restored this incredible species across the South West of England, but in order to do this, it is the right habitat for both the butterfly and the ants which must be maintained. But why is an ant so important to the survival of a butterfly?

One of the most exciting aspects of the Large Blue butterfly, along with its exquisite appearance, is its fascinating lifecycle. The adult Large Blue butterfly has a very short lifespan, only living around 5 days in total. During this time, they must find a partner, mate and lay their eggs in a suitable place – Wild Thyme plants. The pink caterpillar, which will reach around 13mm in length, will hatch from its egg and begin to feed upon Wild Thyme flowers. After it has eaten the first 3 layers of the inner flower, the larva will fall to the floor, waiting for a red ant to find it. An ant, upon finding the larva, will tap it causing the larva to secrete a droplet of sweet liquid from a gland called the ‘Newcomer’s gland’, a process also known as “milking”. The ant will then feed upon this sweet liquid and after 30 – 120 minutes of feeding have passed, the larva pushes itself up using its prolegs causing it to resemble an ant grub. The ant, being fooled by the larva’s appearance, will then carry the larva in its jaws back to its nest and place it with the rest of the ant grubs. These ant grubs are the main source of food for the butterfly larva as it grows and one larva can eat up to as many as 500 grubs during its stay. The butterfly larva will remain underground with the ants for 10 months, forming a chrysalis in its 9th month. Emergence occurs in late June to early July. The butterfly can be identified by the black speckles across its beautiful set of striking blue wings, which are only 16-20mm in length despite the name ‘Large’. This butterfly is amazing to look out when its wings are both closed and open, with shades of blue and black speckles on both the upper and underside of its wings.

Maculineas arion was already considered rare before its initial extinction, however due to stunning aesthetics and rarity, it became extremely popular with butterfly collectors causing a massive reduction in numbers. Scientists also believe that changes in habitat caused issues for the red ants which, in turn, would have had a significant impact upon the butterflies. Due to a myxymatosis outbreak affecting rabbit populations, it is thought that grasslands were not grazed enough to keep the ants happy as they prefer short grass, giving them exposure to the sun. Changes in ant numbers or location would have meant less chance for the butterflies to carry out their full lifecycle.

The reintroduction of the Maculineas arion is mostly down to the work of one man; Professor Jeremy Thomas. It was his pioneering work which first realised the complexities of the lifecycle of the Large Blue  and whilst his discovery was too late to prevent extinction, his work was imperative to the insects’ reintroduction. There is still a lot of work to be done, as the Large Blue is still considered Endangered in the UK, however it is thought numbers are increasing year upon year.  The butterfly is Near Threatened on the IUCN Redlist due to populations across Europe. The numbers are stronger across Europe; however they are thought to be dwindling. The UK distribution of the Large Blue is quite limited, because not only does it require the red ant to survive, but it can only be found in certain types of grasslands and requires Wild Thyme for the larva’s first feed. Finding all of these specifics can be tricky, however thankfully suitable sites were located for its reintroduction. 

One of those sites is Collard Hill in Somerset. The area is a National Trust site and has played a pivotal role in the reintroduction of the Large Blue. So much so in fact, there is a Large Blue hotline, a designated ranger during the summer as well as a team of volunteers and visitors can visit the area to try and catch a glimpse for themselves.
The reintroduction here, which began in 2000, has been very successful. 12 adult females and 3 adult males were released to begin with, followed by 267 larvae shortly after.  In order to keep the site running, there is a lot of year round maintenance which has to occur. It requires strict grazing time’s throughout the year and scrub management to ensure the habitat is just right for both the butterflies and the ants. The blackthorn scrub maintenance is also imperative for the Brown Hairstreak butterfly (Thecla betula), which has also been seen at the site.

It is hoped that as the Large Blue will continue to strive and become one of our wildlife success stories, but in order to do so we must also nurture the poor, duped, red ant.  Myrmica sabuleti is not just fooled by the Large Blue butterfly but is the unfortunate target of other species, namely Zodarion rubidum, an ant-eating spider which feeds solely on red ants. The spider mimics the ants in order ot gain access to them and then feeds on its new friends. This species of spider has not been found in the UK as it was living solely in France, so posed no threat to either Myrmica sabuleti  or Maculineas arion, however the spider has been recently introduced to Central Europe, the US and Canada, so it is certainly a threat to keep an eye on. The future of the Large Blue still hangs in the balance; especially after wet weather in Somerset in 2012 led to a population loss, leaving the species extremely vulnerable. Continuing hard work and research should hopefully secure a positive future for the butterfly and fingers crossed we will never see the loss of 1979 again.  

Loving the Large Blue? Want to help its cause? You can adopt a butterfly from the Somerset Wildlife Trust for £15 – www.somersetwildlife.org/product200.html 

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