Hymenoptera (Insecta) in rural montane habitats – a case study from the Western Rhodope Mountains in southern Bulgaria

Ants, bees and wasps play crucial and various roles in ecosystems and are often used as objects in ecological research in both natural or anthropogenised habitats. This study explores the Hymenoptera diversity from an uncultivated house yard in the mountain hamlet of Grashtitsa at an altitude of 1340 m in the Western Rhodope Mountains in southern Bulgaria. Additionally, data from the vicinities of the village of Patalenitsa (in the foot of the mountain) are also presented. Using pitfall traps, we collected a total of 5189 specimens from 74 species and 22 families, and of them 4695 ex. and 50 species were ants (Formicidae). In Grashtitsa hamlet, with only six traps, between September 2016 and April 2021, we collected 4326 ants from 36 species and 474 ex. from another 21 Hymenoptera families. From the surroundings of the Patalenitsa village, with 16 traps, between May and September 2016, we collected 369 ant individuals from 26 species and 20 more individuals from 12 species of another seven families. The largest numbers of animals were collected in the summer and partially in the spring. The most species-rich ant genera were Lasius (9 species), Formica (8), Temnothorax (6) and Myrmica (5). Some species of conservational or scientific interest were collected (Formica rufa, Lasioglossum anellum, Embolemus ruddii, Messor ponticus). Bethylus cephalotes is firstly reported in Bulgaria and the Balkan Peninsula. Embolemus ruddii, Lasioglossum anellum, Priocnemis confusor, P. hankoi and P. hyalinata are firstly reported for the Western Rhodopes. Spatial distribution reflected the importance of vegetation and hiding places as factors for hymenopterans’ diversity. Over the five-year period of research in Grashtitsa, the Hymenoptera fauna in studied house yard did not show significant qualitative and quantitative impoverishment, or ecological “exhaustion”. This research demonstrates that even small natural habitat patches can harbour a remarkable invertebrate diversity.