Some depressariids have been known since the earliest years of scientific interest in Microlepidoptera. Agonopterix heracliana and A. alstromeriana were described respectively by Linnaeus in 1758 and Clerck in 1759. These are species with larvae that are easily found and reared in early summer; their adults hibernate and in winter are frequently disturbed by human activity such as taking an armful of firewood from the woodshed. By the end of the 18th century 21 European species had been described, many by Denis & Schiffermüller (1775). In the 19th century an additional 88 species were described, initially from the north and central parts of the continent with a number of important contributors including Haworth (1811), Treitschke (1835) followed by Zeller and Stainton and others in the middle part of the century. At this time some species were also described from South Europe notably by Zeller (1847) and Staudinger (1859) but knowledge of the South European fauna always lagged behind central and northern areas. By the end of the century and into the early years of the 20th century increasing numbers of species were being described from the Balkan countries and the Canary Islands, particularly by Rebel over a long period of time. North African species were being described by Chrétien.
The first comprehensive study of genitalia in the family started in 1953 by Hannemann followed by numerous papers including some North African and Asian species, up to 1990. He was able to bring some much needed order to the family with the recognition of numerous synonyms. Towards the end of the century Lvovsky added several species mainly from Russia. In northern Europe there were regional publications covering the family in the Netherlands (Van Laar, 1961, 1964) and Fennoscandia (Palm, 1989). Hannemann (1995) treated the species of Germany, actually covering a much wider area of Central Europe. By the end of the century 160 of the species recognised in the present work were known.
The present century has seen a substantial number of new species described, bringing the European total to 190, many as a result of work for this book, but also by several other authors including Šumpich & Skyva (2012), Šumpich (2013), Rymarczyk, Dutheil & Nel (2013) and Vives & Gastón (2017).
The project to write this book was initiated around 20 years ago when Ole Karsholt asked MC if he would consider the idea. MC was fully aware that he would have limited time and that he lacked the required skills in photography and in making quality genitalia preparations. Nevertheless he accepted the challenge. Initially Ian Thirlwell volunteered to provide the required photographs. Specimens were borrowed from Ian’s neighbour, John Langmaid who also had a keen interest in Depressariidae and from the Natural History Museum, London for description.
Before long, Ian’s circumstances changed and he was obliged to withdraw from the project. It gradually became clear that the project was likely to fail. Fortunately in 2010 Peter Huemer had the idea that PB should collaborate with MC as he had all the skills that MC lacked.
PB’s work on the project has involved the examination of thousands of specimens, genitalia preparations of many hundreds and visits to most of the major natural history museums in Europe. He has also examined many specimens from outside Europe, allowing a better understanding of the European species. He has contributed all the photographs and the distribution table. MC is responsible for most of the descriptive text, but other parts are a collaborative effort.
From the outset we expected to discover previously unknown species from southern Europe, but it was more surprising to find that the well-worked fauna of central Europe also contained undescribed and misidentified species.
While we have been able to solve many problems in the European depressariid fauna, we are aware that there are still unresolved questions and probably some species complexes that need to be untangled. The Depressaria douglasella group is likely to include further species and there are probably additional species related to D. libanotidella. Resolution of these problem groups will entail the study of specimens from many geographical areas, establishing which males and females are conspecific and more information on host-plants.