Notes on digger wasps and potter wasps (Hymenoptera: Bembicidae, Vespidae) in Bulgaria with first record of genus Oryttus

The hymenopteran fauna of Bulgaria is particularly diverse, with one of the main factors being its key location on the border between the Mediterranean and Central Europe. As a result, this country is an important corridor for the migration of many species, especially along natural highways like river valleys and the Black Sea Coast.

Ongoing large-scale monitoring of these corridors, including various sampling methods combined with reviews of observations on citizen science platforms, has resulted in numerous discoveries of generally rare or previously unknown local animal species.

Here, we provide the first documented records of the digger wasp Oryttus concinnus (Rossi, 1790) and the genus Oryttus from Bulgaria, based on six specimens collected over the past three years on the territory of the capital city of Sofia (SW Bulgaria) and photographically documented observations from 2018 in Varna on the Black Sea coast and from 2025 in Sofia.

The potter wasp Rhynchium oculatum (Fabricius, 1781) has a mostly Mediterranean distribution. It was first reported in Bulgaria in Petrich (SW Bulgaria, Struma River Valley) more than 60 years ago. Here, we present a new observation of the species from Rezovo (SE Bulgaria) on the Black Sea coast, near the border of Turkey.

All Bulgarian records of Oryttus concinnus are from towns, supporting the thesis that the open urban areas are particularly suitable for digger wasps and bees because of the warmer microclimate they sustain. The observations of both species show the potential of citizen science groups for the monitoring of changes in the distribution of key species, which could complement traditional research methods tracking the impact of climate change on species distributions.

This study is a part of the project under Grant contract number KP-06-N61/6 – 14.12.2022.