Big-bellied glandular bush-cricket Bradyporus (Callimenus) macrogaster macrogaster (Lefebvre, 1831) is a rare species with severely fragmented populations. It has “Endangered” status on the IUCN Red List and is “Critically Endangered” on the Bulgarian Red Data Book and the European Red List of Orthoptera.

In the period 2021–2023, we set 252 pitfall traps in 42 sampling areas in Western Bulgaria. In four areas we recorded Bradyporus macrogaster. Three of the locations are within the Tri Ushi mountain (near the villages of Bezden, Ponor and Aldomirovtsi). The fourth area is near Breste village, and represents the first locality of this species for Northwestern Bulgaria. The species was previously found there by N. Kodzhabashev in 1989 and 1995, but was not published. This new locality represents a local karst steppe refugium on the edge of the Iskar River Gorge. The river is the only natural ecological corridor crossing the Stara Planina range and contributes to the presence of typical steppe species (Carabus hungaricus, Carabus bessarabicus, common spadefoot toad) in the periphery of the Sofia Basin, the southernmost area from the entire Eurasian steppe biome.

For the first time, the long collection period and the abundant material allow for the establishment of phenological features of Bradyporus macrogaster, its sizes during different instars and of imagoes, and specific diapauses during the year. We also mapped a significant part of steppe bioindicator biota and accompanying species in studied localities.

The localities of the species fall into two Natura 2000 Areas, but the protection of the stenobiont steppe species requires the imposition of highly restrictive conservation measures. Protecting rare species such as the Bradyporus macrogaster is only possible by consolidating the conservation efforts of the entire European community and developing a common strategy for immediate conservation measures that will guarantee the complete integrity of steppe habitats and biota.