Moth found in west London by local resident is a new species to science from Australia

• A moth discovered in a west London park turns out to be a newly described species to science native to Western Australia.
• A specimen of the same type has been sitting undescribed in the Natural History Museum’s collections since 1886.
• The new species has been named Tachystola mulliganae after Barbara Mulligan, the west London resident who found the moth.

A new species of moth to science has been discovered in Ealing, London, by an amateur moth collector. An undescribed moth which had been sitting in the Natural History Museum’s collections, since being collected in 1886 from Western Australia, was a vital piece of the puzzle in establishing that the species had not been recognised by science until now.  

Highlighting the vital role of citizen science - where members of the public are actively engaged with nature and report scientific sightings or findings from their local environment - Barbara Mulligan is the only person in the UK to have found the new species around her local area of west London.

The new species has been named Tachystola mulliganae, after Barbara.

After struggling with classification, Barbara sought the guidance of experts to commence the quest to identify the mysterious tiny brown moth. This team included Mark Sterling, a Scientific Associate at the Natural History Museum, who went on to perform a detailed analysis including both morphology and DNA to describe the species’ anatomy.

‘What Barbara had found was an undescribed species’, said Mark, ‘she found this extraordinary moth which has somehow come over from Western Australia and established itself in three or four places in West London.’

‘And she is still the only person in the UK to have found it. This is a real coup for citizen science.’

Tiny samples of the insect provided researchers with a DNA barcode that allowed them to compare the unknown specimen to a huge database containing the barcodes of thousands of known moth species from around the world. This process revealed that the insect was indeed a new species to science and, in a surprise twist, was one that is native to Western Australia rather than Ealing.

Though it didn’t confirm the identity of the Ealing moth, the DNA barcode told the scientists that it belonged to a group of species that includes the Tachystola hemisema. This moth is found in New South Wales, Australia, and itself has become an invasive species in California, and probably also New Zealand and Hawaii.

The T. hemisema was first described by Edward Meyrick in 1885, whose collection is now cared for by the Natural History Museum.

Accessing and analysing this historical collection led the researchers to the original, or type, specimen from which T. hemisema was named. They also pinpointed an undescribed species that was collected for Meyrick in Western Australia in 1886. 

The investigative journey was solved by the use of state-of-the-art genetic technique known as ‘genome skimming’ by the Natural History Museum, which allows for a specimen’s genome to be sequenced in tiny little fragments.

‘I took a leg of the Meyrick type specimen for Tachystola hemisema from Sydney, and a leg from one of Meyrick’s specimens from Western Australia’, explains Dr David Lees, the Senior Curator for Microlepidoptera at the Natural History Museum.

‘Both of them produced sequences and by adapting existing data analytics programs we were able to read all the data.’

From sequencing the 135-year-old specimens, a conclusion was made that the two moths were genetically distinct and the Ealing moth matched with the undescribed specimen from Western Australia. This conclusion was further strengthened by morphological and anatomical inspection.

‘What David describes is the twenty-first century analysis to determine whether they are the same or different species,’ says Mark. ‘The next stage in satisfying yourself as to whether it is a new species is the rather more old-fashioned nineteenth and twentieth century analysis of looking at the morphology.’

Though the working theory is that the moth travelled to the UK via imported plants, the research team is searching for larvae to confirm how the travelling newcomer wound up in London.

‘Pinpointing an event like this in time and space is quite something and demonstrates the power of modern DNA sequencing and big data analysis,’ says David.

Details of the new moth and the journey of its discovery have been published in Entomologist’s Record and Journal of Variation. 

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