Novel phoretic associations between mites and flies and faunistic composition of phoretic mites at composters in Poland

Mites living in transient and patchy environments frequently spread by phoresy, where many insects serve as carriers. This study aimed to investigate phoresy at compost piles in two orchards, Dąbrowice and Nowy Dwór-Parcela, and a fruit and vegetable farm in Skierniewice, located in the Łódzkie Voivodeship of Poland. Insects and mites were collected in September 2023 using a sweep net and traps. A total of seven associations between mites and flies from the families Drosophilidae, Scatopsidae, Sphaeroceridae, and Chloropidae were recorded. Among them, six phoretic associations, i.e. Macrocheles subbadius on Drosophila immigrans, Lasioseius sp. and Gamasodes spiniger on D. melanogaster, Cornigamasus ocliferius on Leptocera caenosa, Uroobovella fimicola on Coboldia fuscipes and Pediculaster muscarius on Tricimba humeralis, had not been documented previously. The prevalence of mites on netted flies was nearly 4% in the orchards, with the drosophilid fly Drosophila hydei identified as the most prolific carrier. In Skierniewice, the prevalence was 1.5%, and among the netted flies, where only the sphaerocerid Leptocera caenosa was found to carry mites. The phoretic mites captured and recovered from the attractant medium belonged to the Mesostigmata (Macrochelidae, Blattisocidae, Parasitidae, Urodynychidae, Melicharidae), Trombidiformes (Pygmephoridae) and Sarcoptiformes (Histiostomatidae, Acaridae, Suidasiidae), with mesostigmatic mites being the most abundant. Macrocheles subbadius was the dominant species in both orchards, while P. muscarius was the most numerous at the compost pile in Skierniewice.