The entomological collection of the Forschungsinstitut Senckenberg (the Senckenberg Research Institute) in Frankfurt-am-Main currently contains 15,000 series of caddis fly taxa, only a small proportion of which are accurately named larvae. Almost one-third of the material comes from our personal collecting in Sweden and Norway between 1966 and 1990, and from light-trap catches that Prof. Dr. Karl Müller (University of Umeå, Sweden) placed at our disposal for taxonomic and ecological evaluation. The geographic focus of the collections is the east and west coastal areas of the Gulf of Bothnia, Swedish Lapland, and Norwegian Finnmark (see Forsslund & Müller 1962; Göthberg 1973, 1974a/b; Müller 1979, 1982; Tobias, D.1986; Tobias, W. 1968, 1969a/b, 1970, 1972; Tobias, D. & Tobias, W. 1983; Tobias, W. & Tobias, D. 1971, 1976, 1983).

The identification of caddis fly adults from northern Europe was still problematic in the 60s and 70s of the last century, and was largely based on the publications of Martynov, McLachlan, Silfvenius (Siltala), Ulmer and Wallengren. Searches in the scattered specialist literature for suitable aids for the identification of large collections were both complicated and time-consuming, especially as in many cases there were no descriptions of females. For this reason, D. and W. TOBIAS began to build up a personal identification catalogue for the Scandinavian Trichoptera fauna, based on the collections that were available to them. For the majority of species, accurate drawings or photographs were made of the male and female genital armature as well as of ancillary characters, and where necessary these were completed with copies of illustrations taken from the published literature.

According to each person’s individual artistic talents, illustrations of a particular morphological detail can be shown differently or even inaccurately; for example, we need only think of illustrations in the publications of L. Navás. Practice has shown that good photographs, when compared with drawings of the relevant characters, generally lead to more accurate results during the process of identification. Exceptions to this are cases when the internal genital structures are important for the identification of a species or when a precise photographic image has reached the limits of its possibilities due to the small size of the species (e.g. Hydroptilidae).

In the majority of cases the identification of a caddis fly under the microscope can be achieved without preparatory dissection or maceration, and so our photographic images of the genitalia were taken directly from intact specimens. Specimens were photographed layer by layer in dorsal, ventral and lateral views, using the binocular microscope LEICA MZ 12 with an OLYMPUS DP-12 digital camera system. The individual series of imaging data with their different depths of field were then recombined on the computer using imaging system software ADOBE Photoshop CS2 in order to obtain a sharp, three-dimensional, colour or black-and-white picture.

Although there has been no lack of good identification keys for European caddis flies in recent times, especially the Atlas by Malicky (2004), it nevertheless seemed to us to be sensible to make the results contained in our reference work, which has been made increasingly comprehensive over the years, available to other caddis fly workers as a freely available internet publication.

This website contains illustrated dichotomous and synoptic identification keys to the twenty caddis fly families occurring in the Fennoscandian region. Clicking on a coloured family name will provide a link to a systematic list of the taxa included in that family, in which each species name is linked to an actual identification page for the species. This web page contains brief information on the distribution, the level of threat that the species may face (graded according to IUCN Red Lists), and a plate with the identification characters for males and females. Unfortunately, illustrations from the literature have had to be used for some species because no original material was available. The bibliography contains a large number of older and more recent taxonomic, ecological and zoogeographic publications on the caddis flies of Scandinavia, but is certainly incomplete.

The advantage of an on-line publication is that the data can be updated at any time. For that reason we ask users to inform us of errors, additions, and suggestions for improvement, so that we can make the necessary corrections.