Rooms available for wild bees and other insects

They are small, quiet and usually inconspicuous, yet their contribution to life as we know it is enormous. Wild bees, bumblebees, digger wasps and many other insects belong to the so-called Hymenoptera, one of the most species-rich groups of insects in Central Europe. As pollinators, they not only ensure plant diversity but also control pests. Yet many of these species can hardly find suitable habitats in our cities anymore. Modern building facades often lack the small cracks and crevices that used to serve as nesting sites. Rotten trees, dead branches or old fence posts have also become rare in built-up areas. The loss of such natural structures is a factor in many of these beneficial insects now being on the Red List.

A simple and effective measure to protect these creatures is the provision of nesting aids for insects. These can be made from natural and carefully selected materials such as hardwood with smooth drill holes, small tubes of reed or bamboo, filled clay bricks or loose sand, and offer a variety of small spaces for different species. What matters is not the size, but the quality and variety of nesting options. Each species has its own requirements regarding shape and material. For instance, wild bees require specific tube diameters for egg-laying, whilst solitary wasps prefer to nest in sandy tubes. One example of such an inhabitant is the steel-blue mason bee (Osmia caerulescens). It is found in structurally diverse landscapes as well as in cities, provided it can find sufficient flowers and suitable tubes for nesting.

On the University of Graz campus, such insect hotels are specifically placed where they are most useful. The locations are sunny, sheltered from the wind and situated near areas rich in flowers. This is because without a sufficient supply of native flowering plants that provide food from early spring through to late summer, even the best nesting aid remains unused. Early-flowering plants play a particularly important role here, as many wild bee species are already active in March. What at first glance looks like a simple wooden box thus becomes an entire micro-ecosystem making a valuable contribution to biodiversity.