Regularly updated "Red lists" provide an important tool to monitor populations of rare and vulnerable species. The decision to include certain species and assign it certain category is usually made by experts on the basis of the available data on the current status of its populations in the region. Special criteria are developed by IUCN, allowing to assess the status of the population by quantitative characteristics (e.g. decline in the size of the population, decline in the area of distribution or area of occupancy). However, for many organisms (including insects) application of these criteria may be difficult, especially in poorly studied areas. When the size of the population (for example, "the number of mature individuals") is rather difficult to calculate, it may be possible to determine the area of distribution indirectly, by estimating the area of suitable habitats.
The last edition of Red Data Book of Karelia includes 272 insect species. Great part of them (about 60%) are typical forest inhabitants. Many of these species are dependent on decaying wood and survive only in aged, naturally growing forests. It should not be a problem to estimate approximately the total area of such forests basing on the forestry data and similar approach is possible for other habitat types. So, in some cases we could really use IUCN criteria even for poorly studied taxa. Nevertheless, it should be noted that Red Data Books of Russian regions aimed to legally fix protected status of the species, while the "Red lists" of European countries just estimate the species vulnerability. In this respect, direct application of the IUCN criteria in the Russian Red Data Books (in their current implementation), may be impractical.
A.Polevoi Rare insects of Karelia and their habitats