Invasive moth on garden conifers identified

This story starts with a Dutch amateur moth collector, Jaap van Vuure, who found from 1984 onwards an unknown species of Argyresthia in his village Kortgene (province Zeeland), commonly flying around Thuja species. He identified this moth as Argyresthia reticulata, a species described from the Swiss Alps and also known from France, where it was recorded on the rare Juniperus thurifera. This species has since been observed in several localities in the Netherlands, and much later (2009) also in Belgium. 

In 2019, a similar moth was found in the region of Paris, France, but as by then DNA barcoding had become popular, its barcode was analysed and compared with data in the global Barcode database BOLD. This led to a match with Canadian specimens collected in 2006 that were identified as the North American Argyresthia freyella. The French collectors therefore recorded this species as new for Europe.

Canadian moths

However, the Canadian locality of the barcoded specimens was remarkable, namely Surrey, a suburb of Vancouver, British Columbia. These specimens were collected on ornamental junipers edging a shopping mall parking lot. Until then A. freyella was known as an eastern North American species, associated with juniper. When Naturalis researcher Erik van Nieukerken compared photos of the species discussed above with that of the holotype of A. freyella, he noticed big differences in the external characters: whereas the type of A. freyella has a distinct black dot in the forewing tip and a white thorax (see photo above), the specimens from Vancouver have neither character. Thus, they could not be A. freyella, and the specimens from BOLD had to be misidentified. This was confirmed by collector Jean-François Landry, who had just made a tentative identification for this sample. Taxonomic expertise therefore remains indispensable in the age of barcodes!

Junipers

Back to the Dutch-French moths. Our species also could not be A. reticulata, which the French authors already had concluded correctly, based on size and genitalia. This can also be inferred from the life history. The invasive species is a leafminer of Thuja and Juniperus, whereas A. reticulata feeds on the berries of Juniperus.

Meanwhile the DNA-barcodes of specimens from Belgium and the Netherlands had also been checked, and they share the barcode with the specimens from Paris and Vancouver. This showed how important the global database of DNA-barcodes is, as we found an almost match with some specimens from China, Shandong. They were analysed by researcher Liu Tengteng from Shandong Normal University, who had in his research on this genus until then not been able to make a final identification of these specimens, that were reared from Platycladus orientalis and Juniperus chinensis.

Concluding 

On the basis of study of the morphology, we have identified the invasive species as Argyresthia sabinae, described from Japan, where it was found feeding on Juniperus procumbens. A scientific paper, dealing with these species, is currently in preparation.

As we needed a name for this species for a forthcoming book on Dutch micromoths, and don’t want to let the misidentifications continue to be used, we present here our tentative conclusion on the identity. 

Distribution and life history of Argyresthia sabinae 

Apart from the original record from Japan, Kyushu, we have now positive records with DNA-barcode data from the Netherlands, Belgium, France, and Canada (British Columbia). It is especially common in Belgium and less so in the Netherlands. Tentatively we consider also the Chinese specimens to belong to this species. Two records from near Boston and New York in the United States are also probably this species. 

The species apparently feeds on a number of conifer species from the Cypress family: Juniperus procumbens (Japan), Juniperus spec. (Belgium), Juniperus chinensis (China), Platycladus orientalis (China) and Thuja occidentalis (Netherlands). The larva makes mines in the needles or leaves in wintertime, and leaves the mine between January and March to pupate in a cocoon on the plant or on the soil. Adult emergence occurred from March to April, in nature moths were found from late April to mid-June.

It is likely that this species has been spread with its host plants, which are extensively shipped all over the world. This could have been as eggs, larvae or cocoons. The species has nowhere been a problem, and does not seem to occur in high densities.

More information

• Article: Argyresthia freyella Walsingham, 1980, espèce nouvelle pour la France et l'Europe (Lepidoptera, Argyresthiidae).
• DNA-barcodes.

Text: Erik J. van Nieukerken, Naturalis Biodiversity Center; Jean-François Landry, Canadian National Insect Collection; Liu Tengteng, Shandong Normal University; Sadahisa Yagi, Kyushu University; Tymo Muus, Microlepidoptera.nl
With contributions by Nick Peeters, Jan Soors and Dave Holden
Photos: Jan Soors (lead photo: Argyresthia sabinae); David Reed; Microlepidoptera.nl; Carina Steenwinkel; Jean-François Landry; Liu Tengteng; FinBOL