Memoranda Societatis pro Fauna et Flora Fennica

Nationwide survey of social wasps (Vespinae) in Finland

Atte Komonen — 2025-04-06

Global change affects species distribution and abundance. To monitor changes in the distribution and abundance of social wasps (Vespinae), reliable baseline data are needed. We established a network of study sites (n = 16) to study vespine abundance throughout Finland, ranging a 1 100 km south to north distance, during 2019–2024. Similar beer traps were used in all sites. Altogether 4 099 individuals and nine species were captured. The most abundant and frequent species was Vespula vulgaris (60% of individuals and 92% site-year occupancy) followed by Dolichovespula media (31% and 81%) and Vespa crabro (3% and 4%). Vespa crabro was only trapped in Åland Islands, but abundantly. Variation in the abundance of V. vulgaris and D. media was great among sites and years. Our study suggests great spatio-temporal variation and species-specificity in beer trap catches of social vespine wasps, which should be considered in designing monitoring protocols.

Succession of land snails (Gastropoda) in the Finnish Archipelago Sea

Irene Routio — 2025-04-07

The Finnish southwestern archipelago, or the Archipelago Sea, consists of 40 000 skerries and islands, so more than in any other archipelago in Europe. Four species of land snails (Gastropoda) were found on skerries sized 100 to 500 m², seven species were found in the group of 500 to 1 000 m² -sized skerries, 21 were found on isles of 3 to 10 hectares, and 33 species were found on islands of 400 to 1 040 hectares. In total, 9 722 individuals from 36 different species were found. The smallest skerry from which land snails were found had an area of 298 m² and only one species, Oxyloma elegans.

The occurrence of Fucus vesiculosus algae walls in islands is an important regulating factor for land snails in the Finnish archipelago. Dead algae-matter is brought to shore by waves. Tall, long, decomposing walls of F. vesiculosus form an important microhabitat for land snails. Bird skerries are not a favorable environment for land snails due to the small amount of soil available and its high usage and consumption by birds. The height of the island is not a primary factor in the lives of land snails.

Species specialized and adapted to the harsh conditions of the archipelago are Oxyloma elegans, Pupilla muscorum and Balea perversa. Even small skerries have occurrences of Clausilia bidentata and Cochlicopa lubrica. Oxyloma elegans was observed following r-strategy for reproduction. No endemic species were found. A peculiarity was Cochlicopa lubrica’s black form repentina.

A note on the expansion of the Eurasian nuthatch (Sitta euopaea) on the Åland Islands

Ralf Carlsson — 2025-04-07

This paper gives a brief description of the Eurasian nuthatch Sitta europaea; appearance and habits. From being an absent bird in the Alandian bird fauna, it started to appear around 2008 and has expanded its range in the years that followed. The reason for its rapid expansion is likely a result of the warmer climate as the species has expanded its range also in Sweden and the UK.