Bucculatrix brunnella sp. n. is described from Sicily and Sardinia. The male of the new species is characterized by the almost monochrome ochreous brown forewing. It may resemble the monochrome form of B. cristatella (Zeller, 1839), but the colour of the forewing of the latter species is pale ochreous grey. The female of the new species is slightly smaller, paler and with more conspicuous pattern on the forewing than those of the male. B. brunnella sp. n. differs markedly in the male genitalia from other known Bucculatrix species. The immature stages are unknown. The male and female adults, and genitalia of both sexes, are figured and a distribution map is provided.

About 300 species of the family Bucculatricidae are known worldwide, the great majority of which belong to the genus Bucculatrix Zeller, 1839. From the Nearctic region 103 species from this genus are listed by Pohl et al. (2018), approximately the same number occur in the Palaearctic region, and 55 species of these are currently recognised in Europe (Baryshnikova 2013; Mey 2013; Tokár 2017).

Bucculatrix adults are usually very similar in coloration and forewing pattern and, moreover, differences in the genitalia structures in closely related species are often small. For these reasons, and with the significant contribution of genetic analyses, it can be expected that the number of European species will be higher.

However, species which are distinctly different from other known species are found rarely within the European fauna of this genus. One such species was found on the Italian islands of Sicily and Sardinia.

During two visits to Sicily in June 1995 and 2000, when the second author with his brother Zdeněk catalogued the Lepidoptera fauna of the island, they found several males of an unknown Bucculatrix species at three localities in the vicinity of Mount Etna. Some years later, specimens of the unknown species were given to the first author for detailed study. An examination of these males showed that they belonged to a hitherto undescribed Bucculatrix species.

The first author attempted to obtain additional material, especially a female of this species from other private and museum collections. He found two more males in the Klimesch collection (Zoologische Staatssammlung München). Later, he finally obtained through Dr Paolo Triberti (Museo Civico di Storia Naturale in Verona) two females, one of which is from Sicily and second from Sardinia.

Thus, after obtaining both sexes, it was possible to proceed to the description of the new species.

All specimens of the new species were taken as adults, most of them having been attracted to light-traps.

The genitalia were dissected in the usual way for small Lepidoptera, the preparations being stored in glycerol in small plastic vials or embedded in Euparal on glass slides. The drawings of the adults were made by the second author using water colours. Drawings of the genitalia were made by the first author using Indian ink on transparent sheets.

The discovery of Bucculatrix brunnella sp. n. shows that the Mediterranean fauna of European Bucculatricidae is still insufficiently studied and can provide surprises. Despite the isolated geographic occurrence in Sicily and Sardinia, it can be assumed that the species lives also on Corsica or on other nearby islands in the Mediterranean Sea.

According to morphological characters the new species belongs to a large B. gnaphaliella (Treitschke, 1833) species group consisting of more than 100 species worldwide (Baryshnikova 2013).

In their development, species from the group specialized mostly on flowering plants in the Asteraceae. There are numerous closely related and morphologically poorly distinguishable species within this and other groups of Bucculatrix, suggesting that their differentiation occurred comparatively recently. Baryshnikova (2016) supposes that such differentiation is associated with the rise of dissimilarities in the mechanisms of attraction of individuals of the opposite sex and/or using different host-plants, but considers that it is difficult to know which evolutionary changes appeared first to trigger the speciation process.

For our new species it is obvious that its isolation from the mainland facilitated its speciation which resulted (as in the recently described species B. kaptarae Tokár, 2017 from Crete) in a higher degree of morphological differences from related species. We can only assume that – according to some of its morphological features and of the continental species B. humiliella Herrich-Schäffer, 1855 – they had a common ancestor before the separation of Sardinia and Sicily from their adjacent mainland.

Our thanks are due to Paolo Triberti (Verona, Italy) and Andreas Segerer (Munich, Germany) for providing specimens. The former also kindly provided genitalia slides and added valuable comments on the manuscript. Peter Huemer (Innsbruck, Austria) and Zdeněk Laštůvka (Brno, Czech Republic) are acknowledged for their advice on the manuscript. We thank Marko Mutanen (Oulu, Finland) for his assistance in carrying out the DNA analysis, and Robert J. Heckford (Plympton, U.K.) for checking and correcting the English of the manuscript and for helpful comments.