Collaboration

Birna V. Trygvadóttir Fjallstein
(Biofar, FO)

Karl A. Thomsen
(Syðrugøta, FO)

Vladimir Gusarov
(Natural History Museum,
University of Oslo, Norway)

Arne Fjellberg
(Tjörne, Norway)

Invertebrates of Koltur

The invertebrate communities on Koltur are a good representation of the native Faroese invertebrate fauna. There are few herbivores, and omnivorous and predatory taxa such as carabid and staphylinid beetles, spiders, and harvestmen dominate on the ground. Flies are the overwhelming majority of flying insects, both in terms of abundance and number of species. Koltur is special in that it has not yet been occupied by invasive invertebrate species such as the New Zealand flatworm and the Spanish slug, thus supporting supposedly intact native invertebrate communities.

MAIN INVERTEBRATE GROUPS

Beetles (Coleoptera)

Since the start of the project in 2019, at least 45 species of beetles were found on Koltur, which represents around 25% of the known beetle fauna of the whole of the Faroes.

Most species belong to the families Carabidae (ground beetles) and Staphylinidae (rove beetles). The most abundant species in the pitfall traps are Loricera pilicornis, Patrobus septentrionis (both Carabidae), Tachinus signatus, and Quedius nitipennis (both Staphylinidae). Widespread but less numerous are Nebria salina, Notiophilus biguttatus, Trechus obtusus (all Carabidae), Stenus brunnipes, Othius angustus, and Cypha laeviuscula (all Staphylinidae).

A few species of Curculionidae (weevils) have been found so far, among them Otiorhynchus arcticus, Otiorhynchus nodosus, Barynotus squamosus, Tropiphorus obtusus, and Apion haematodes.

Common beetles in sheep dung are Aleocharinae (Staphylinidae), Cercyon haemorrhoidalis and Megasternum concinnum (Hydrophilidae), as well as the dung beetles Aphodius ater and A. borealis (Scarabaeidae). The latter species was recently discovered on Koltur as a new beetle record for the Faroes.

Flies (Diptera)

About 25% of all insects in the Faroes are Diptera, belonging to 45 different families. They are also the most species rich insect group on Koltur. However, identification can be challenging and there are most likely more species present than recorded so far.

Commonly associated with sheep dung and present all over the island is the yellow dung fly Scathophaga stercoraria. Although it might be the most conspicious saprophagous species on Koltur, there are many other flies which use the omnipresent sheep dung as a resource, for example in the families Anthomyiidae, Phoridae, and Sphaeroceridae.

Other common flies on the island are Mycetophilidae, Tipulidae, Limoniidae, Cynomya mortuorum (Calliphoridae), and Lonchoptera lutea (Lonchopteridae).

Chironomidae larvae live in the shallow waters of the small streams, and their adults can be seen swarming in the vicinity. The slow-running streams in the lowland areas are inhabited by Tanytarsus sp. and Micropsectra atrofasciata, whereas the streams on the steep Northern slopes contain among others Tvetenia calvescens, Eukiefferiella spp., Diamesa incallida, and Macropelopia nebulosa. Halocladius fucicola, a Chironomid species adapted to brackish water, lives in the tidal pools at the Southern shore of Koltur.

*Scathophaga stercoraria* (Scathophagidae)

Other Insects

Forficula auricularia (Dermaptera) is occasionally found in pitfall traps, as well as Arctorthezia cataphracta (Hemiptera), small Hymenoptera and Collembola. Larvae of caddis flies (Trichoptera) live in the small streams on Koltur, and their adults can be seen in the vicinity.

Other Invertebrates

The black colour morph of Arion ater (Gastropoda) is common on the island, especially on the Northern side.

Due to the absence of the invasive New Zealand flatworm (Arthurdendyus triangulatus; Platyhelminthes), earthworms are more abundant on Koltur than elsewhere in the Faroes, and at least seven species of earthworms (Lumbricidae) have been reported.