Heterocerini MacLeay 1825* Heterocerus fenestratus (Thunberg, 1784) (Plate IV, 43)New data: W of Srem Vill., about 100 m from Tundzha River, 42°02.996′N 26°28.272′E, 84 m a.s.l., meadows, 07.vi.2020, 3 ♂♂ (BFUS- COL000420 – BFUS-COL000422), 4 ♀♀ (BFUS- COL000423 – BFUS-COL000426), at light (white & UV), Y. Petrova leg.; Ustrem Vill., about 150 m from Manastirska Reka River, 42°01.332′N 26°27.381′E, 100 m a.s.l., house yard, 11.vii.2020, 1 sex indet. (BFUS-COL000427), at light (UV), D. Gradinarov & Y. Petrova leg.; the same locality, 15.vii.2020, 1 ♀ (BFUS- COL000428), at light (white & UV), D. Gradinarov & Y. Petrova leg.; the same locality, 05.ix.2021, 1 ♂ (BFUS- COL000429), at light (UV), D. Gradinarov & Y. Petrova leg.; the same locality, 28.vi.2022, 2 ♀♀ (BFUS- COL000430, BFUS-COL000431), at light (UV), D. Gradinarov & Y. Petrova leg.; the same locality, 09.ix.2024, 1 sex indet. (BFUS-COL000432), at light (UV), D. Gradinarov & Y. Petrova leg.; W of Ustrem Vill., near Manastirska Reka River, 42°01.452′N 26°27.094′E, 103 m a.s.l., riverine vegetation, small swamp, 12.vii.2020, 2 ♀♀ (BFUS- COL000433, BFUS-COL000434), at light (white & UV), D. Gradinarov leg.; the same data, 42°01.449′N 26°27.084′E, 101 m a.s.l., 2 ♂♂ (BFUS- COL000435, BFUS-COL000436), 3 ♀♀ (BFUS- COL000437 – BFUS-COL000439); the same data, 42°01.448′N 26°27.083′E, 100 m a.s.l., 13.vii.2020, 5 ♂♂ (BFUS- COL000440 – BFUS-COL000444), 8 ♀♀ (BFUS- COL000445 – BFUS-COL000452), 5 sex indet. (BFUS-COL000453 – BFUS-COL000457); W of Srem Vill., about 50 m from Tundzha River, 42°02.890′N 26°28.360′E, 87 m a.s.l., dirt road, agricultural fields, 16.vii.2020, 1 ♂ (BFUS- COL000458), 3 sex indet. (BFUS-COL000459 – BFUS-COL000461), at light (white & UV), Y. Petrova leg.; W of Srem Vill., right bank of Tundzha River, 42°02.890′N 26°28.438′E, 85 m a.s.l., riverside meadows, 16.vii.2020, 3 ♂♂ (BFUS-COL000462 – BFUS-COL000464), 4 ♀♀ (BFUS- COL000465 – BFUS-COL000468), 5 sex indet. (BFUS-COL000469 – BFUS-COL000473), at light (white & UV), D. Gradinarov leg.; W of Ustrem Vill., near Manastirska Reka River, 42°01.451′N 26°27.060′E, 98 m a.s.l., riverside meadows, 20.vii.2021, 1 ♂ (BFUS- COL000474), at light (white & UV), D. Gradinarov leg.; the same data, 42°01.450′N 26°27.093′E, 101 m a.s.l., riverine vegetation, small swamp, 22.vii.2021, 2 ♂♂ (BFUS- COL000475, BFUS-COL000476); the same locality, 24.vii.2021, 2 ♂♂ (BFUS- COL000477, BFUS-COL000478), 3 ♀♀ (BFUS- COL000479 – BFUS-COL000481), 10 sex indet. (BFUS-COL000482 – BFUS-COL000491), at light (UV), D. Gradinarov leg.; W of Ustrem Vill., near Manastirska Reka River, 42°01.448′N 26°27.022′E, 98 m a.s.l., riverside meadows, 23.vii.2021, 4 ♂♂ (BFUS- COL000492 – BFUS-COL000495), 3 ♀♀ (BFUS- COL000496 – BFUS-COL000498), 5 sex indet. (BFUS-COL000499 – BFUS-COL000503), at light (UV), D. Gradinarov leg.; the same data, 42°01.417′N 26°27.140′E, 102 m a.s.l., riverine vegetation, small swamp, 29.vi.2022, 1 ♀ (BFUS- COL000504), at light (white & UV), D. Gradinarov leg.; the same data, 42°01.406′N 26°27.161′E, 97 m a.s.l., riverine vegetation, meadows, 21.vi.2023, 1 ♂ (BFUS- COL000505), 1 ♀ (BFUS- COL000506); W of Srem Vill., right bank of Tundzha River, 42°02.935′N 26°28.359′E, 80 m a.s.l., riverine vegetation, 11.vii.2025, 7 ♂♂ (BFUS- COL000507 – BFUS-COL000513), 5 ♀♀ (BFUS- COL000514 – BFUS-COL000518), at light (white & UV), D. Gradinarov & Y. Petrova leg.* Heterocerus fusculus fusculus Kiesenwetter, 1843 (Plate IV, 44)New data: W of Ustrem Vill., near Manastirska Reka River, 42°01.449′N 26°27.084′E, 101 m a.s.l., riverine vegetation, small swamp, 12.vii.2020, 1 ♂ (BFUS- COL000519), 6 ♀♀ (BFUS-COL000520 – BFUS-COL000525), at light (white & UV), D. Gradinarov leg.; the same data, 42°01.452′N 26°27.094′E, 103 m a.s.l., 4 ♀♀ (BFUS- COL000526 – BFUS-COL000529); the same data, 42°01.448′N 26°27.083′E, 100 m a.s.l., 13.vii.2020, 1 ♂ (BFUS- COL000530),1 ♀ (BFUS-COL000531); W of Srem Vill., about 50 m from Tundzha River, 42°02.890′N 26°28.360′E, 87 m a.s.l., dirt road, agricultural fields, 16.vii.2020, 1 ♂ (BFUS- COL000532), 2 ♀♀ (BFUS- COL000533, BFUS-COL000534), at light (white & UV), Y. Petrova leg.; W of Srem Vill., right bank of Tundzha River, 42°02.890′N 26°28.438′E, 85 m a.s.l., riverside meadows, 16.vii.2020, 4 ♂♂ (BFUS- COL000535 – BFUS-COL000538), 2 ♀♀ (BFUS- COL000539, BFUS-COL000540), at light (white & UV), D. Gradinarov leg.; W of Ustrem Vill., near Manastirska Reka River, 42°01.450′N 26°27.093′E, 101 m a.s.l., riverine vegetation, small swamp, 22.vii.2021, 1 ♂ (BFUS- COL000541), 1 ♀ (BFUS- COL000542), at light (white & UV), D. Gradinarov leg.; the same locality, 24.vii.2021, 5 ♂♂ (BFUS- COL000543 – BFUS- COL000547), 1 ♀ (BFUS- COL000548), 1 sex indet. (BFUS-COL000549), at light (UV), D. Gradinarov leg.; the same data, 42°01.448′N 26°27.022′E, 98 m a.s.l., riverside meadows, 23.vii.2021, 4 ♂♂ (BFUS- COL000550 – BFUS-COL000553), 4 ♀♀ (BFUS- COL000554 – BFUS-COL000557), 7 sex indet. (BFUS-COL000558 – BFUS-COL000564); the same data, 42°01.417′N 26°27.140′E, 102 m a.s.l., riverine vegetation, small swamp, 29.vi.2022, 1 ♂ (BFUS-COL000565), 1 ♀ (BFUS- COL000566), at light (white & UV); W of Srem Vill., right bank of Tundzha River, 42°02.935′N 26°28.359′E, 80 m a.s.l., riverine vegetation, 11.vii.2025, 2 ♂♂ (BFUS- COL000567, BFUS-COL000568), 2 ♀♀ (BFUS- COL000569, BFUS-COL000570), at light (white & UV), D. Gradinarov & Y. Petrova leg.Notes: The species is not listed for Bulgaria in both editions of the Catalogue of Palaearctic Coleoptera (Mascagni 2006, 2016). Greń & Lubecki (2017) reported this species from Primorsko, Black Sea coast (as Heterocerus fusculus Kiesenwetter, 1843).A total of 50 beetle species from 12 families from the Bulgarian part of the Sakar Mountain are included in the prepared list. Representatives of all three suborders of Coleoptera with aquatic species (Myxophaga, Adephaga and Polyphaga) are found in the area of the mountain. Despite the observed species diversity, the water beetles of the Sakar Mountain are still insufficiently studied. Special attention in future research should be paid to the species inhabiting permanent and temporary ponds, as well as those from the Tundzha and Maritsa rivers. It is also desirable to study the habitat preferences of the water beetles found in the territory of the mountain.