A new species of insect has been discovered among more than 1,000 rare creatures catalogued for a survey of the Cairngorm Mountains in Scotland.
The Christii fly was discovered living in the bark of a tree
The results of the study are included in a book launched by Scottish Natural Heritage on Monday.
The tiny black Christii fly measures just 2mm long and lives under the bark of dead aspen trees.
Another 20 plants, invertebrates and fungi species found were also new to Britain and some were new to science.
The book, The Nature of the Cairngorms, also includes 223 species mainly found in the area and some 1,150 species for which the mountains are nationally important.
Professor Des Thompson, SNH uplands adviser and a contributor to the book, said: "Nowhere else in Britain, and some would argue in Europe, will you find so much diversity of wildlife in such a confined area.
"The book highlights the particular importance of the Cairngorms' woodland habitats, and the area's less well-known species, such as its insects, fungi and lichens."
The book, being launched in the Cairngorms National Park, contains research carried out over the past 20 years and has contributions from 35 authors.
The survey covers everything from slow worms to dragonfly
The mountains' more iconic species include the capercaillie, ptarmigan, freshwater pearl mussel, pine marten and red squirrel.
SNH said the incredible diversity was partly a result of the ancient Caledonian forest, which provides a refuge for many species not found elsewhere.
The richest concentrations were in the woodland areas, particularly the Strathspey forests of Abernethy, Rothiemurchus and Craigellachie to Coylumbridge, as well as parts of Deeside.
It is hoped the book will encourage more research in other important wildlife areas in Europe.
The Christii fly (Ectaetia christii) was discovered under the bark of a fallen aspen tree near Grantown in 1997 by Graham Rotheray of the National Museum of Scotland and Dave Horsfield of SNH.
Mr Rotheray said: "This is a superb example of a boreal species which has laid undiscovered in Scotland for thousands of years.
"We have since found it again two or three times in the Cairngorms and it has recently been discovered in Norway.
"It is a specialist species which adapted and probably came north with the retreat of the ice."
SNH said conserving and enhancing the national park's biodiversity and landscapes was a key priority in developing the National Park Plan for the Cairngorms, which is out for consultation at the moment.