﻿Diversity of flesh flies (Sarcophagidae, Sarcophaginae) of pond habitats in rural areas in the Croatian part of Baranja

﻿Abstract The diversity of grey flesh flies (Sarcophagidae: Sarcophaginae) from the Croatian part of Baranja was studied during 2019 to 2021, resulting in 37 species, of which the following are new for the area: Raviniapernix (Harris, 1780); Sarcophaga (Het.) depressifrons Zetterstedt, 1845; S. (Het.) filia Rondani, 1860; S. (Het.) haemorrhoides Böttcher, 1913; S. (Het.) pumila Meigen, 1826; S. (Het.) vagans Meigen, 1826; S. (Lis.) dux Thomson, 1869; S. (Lis.) tuberosa Pandellé, 1896; S. (Meh.) sexpunctata (Fabricius, 1805); S. (Pan.) protuberans Pandellé, 1896; S. (Sar.) carnaria (Linnaeus, 1758); S. (Sar.) variegata (Scopoli, 1763), and S. (Pse.) spinosa Villeneuve, 1912. New locality records are provided for 25 species. Sarcophaga (Sar.) croatica Baranov, 1941 was the most abundant with 37%, followed by S. (Sar.) lehmanni Müller, 1922 (21%), and S. (Pas.) albiceps Meigen, 1826 (5%), making up 63% of all collected specimens. Most species (35) were collected in locality of Zmajevac, while the fewest (3) were collected in Bilje locality. During this study, S. (Pse.) spinosa was recorded in Croatia for the first time. Combined with previous records, 42 species of flesh flies have been recorded from Croatian Baranja, which comprise 27% of the flesh flies known to occur in Croatia. The total number of species of the family Sarcophagidae currently known in Croatia has increased to 156.


Study area
Baranja is a Pannonian Plain region of Hungary (its northern portion) and Croatia (its southern portion). It is situated in the eastern part of Croatia and forms part of Osijek-Baranja County. Triangular in shape, it covers an area of 1147 km 2 between the Drava, the Danube, and the state border with Hungary (Bognar et al. 1975). The Croatian part of Baranja is a predominantly lowland area (elevation ≤ 259 m). Bansko brdo (Bansko Hill) is the most prominent part of Baranja in terms of relief and extends NE-SW for 21 km, whereas its width is much smaller (Bognar et al. 1975). The steppe, the natural vegetation that covers Bansko Hill, has completely disappeared. The belt along the Danube and Drava is a flooded area (~ 63% of the territory) with many secondary tributaries and wetlands (Kopački rit) (Bognar et al. 1975). The Kopački rit Nature Park is one of the largest fluvial-marshy plains in Europe (Schneider-Jacoby 1994), and the basic ecological features relate to the river dynamics (Schneider-Jacoby 1994;Mihaljević et al. 1999). Forests cover ~ 20% of the Croatian part of Baranja. The climate is moderately continental with significant temperature fluctuations. The average January temperature is ~ -1.3 °C, and the July temperature is ~ 22 °C; the average annual rainfall is ~ 650 mm (Bognar et al. 1975). The Croatian part of Baranja contains 54 settlements, some of which contain pond habitats, which increasingly serve as places for recreation of people and their pets. All seven sampling sites are situated at the periphery of the settlements (Fig. 1). Geographical coordinates of these seven sampling sites are given in Table 1. Pond habitats in settlements of Kotlina, Suza, and Zmajevac are surrounded by species of willow (Salix) and poplar (Populus). Sampling sites in the settlements of Petlovac and Popovac are overgrown mainly with reeds (Phragmites australis), sedges (Carex ssp.), and rush (Typha ssp.) without forest vegetation at its edges. A similar type of vegetation is present at the pond in Darda, with the addition of water lilies (Nymphaea alba) and nenuphar (Nuphar luteum), while pond habitats in Bilje settlement are overgrown with different species of low grasses exposed to the open sun throughout the day.  Darda;3. Kotlina;4. Petlovac;5. Popovac;6. Suza;7. Zmajevac.

Sampling and identification
Collections of sarcophagids from pond habitats were made frequently over a period of seven months (April-October) from 2019 to 2021. During 2019 and 2020, from April to October, sampling at the pond habitat in Zmajevac was done 1-5 times a month. Samplings in 2021 were carried out once per month from May to August. Flesh flies were sampled from 1 pm to 5 pm using a standard insect sweep net to selectively collect flies resting on soil and vegetation, or attracted to animal faeces and the remains of discarded food. The collected specimens were preserved in 96% ethanol. Male terminalia were prepared for species identification following the method of Richet et. al (2011). After two days in ethanol, male abdomens were dissected and soaked in a 10% KOH solution for 72 h. They were then immersed in 10% acetic acid for 1 min and rinsed with water for 1 min. They were then dehydrated in beech-wood creosote for 4 h. The phallus, pregonites and postgonites, sternite 5, cerci, and surstyli were separated from the rest of abdomen and placed into a plastic vial (volume of 2 ml) with 96% of ethanol solution. Identifications were carried out using keys for Sarcophagidae (Pape 1987;Povolný and Verves 1997;Richet et al. 2011) and descriptions and illustrations in Whitmore (2009Whitmore ( , 2010Whitmore ( , 2011 and Whitmore et al. (2013). Nomenclature and classification follow the Fauna Europaea database (Pape 2004). For all samples, the following information is provided: locality and date of collection, collector(s), number and sex of specimens, and depository. Also, 33 unidentified specimens from May 2018 are now identified and their data have been included in this study. One species newly recorded for the Croatian fauna is marked with a black triangle (▲). Specimens examined for this study are deposited in the collections of the Department of Biology, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia (DBUO) and the Staatliches Museum für Naturkunde, Stuttgart, Germany (SMNS).

Terminology
Subgeneric names are abbreviated as follows:

Results
A total of 1293 flesh flies belonging to 37 species was collected (Table 2). Sarcophaga (Sar.) croatica Baranov, 1941 was the most abundant with 37%, followed by S.  (Table 2). Most species (35) and specimens (75%) were collected in Zmajevac ( Table 2). The lowest number of species was collected in Bilje (3), whereas in other localities the number of collected species was between 8 and 11. The largest number of specimens and species was collected during 2019 (Table 3). New records for Baranja are provided for 25 species, with the record of S. (Pse.) spinosa representing a first record for Croatia.

Sarcophaga (Heteronychia) pumila Meigen, 1826
New records for Croatian Baranja. Popovac, 11.VI.2021 Baranov, 1941 (1♂) (DBUO); Kotlina, 18.VI.2021 (Povolný and Verves 1997), whereas one, S. (Het.) pseudobenaci, is restricted to southeastern Europe (Pape 2004). Sarcophaga (Pse.) spinosa represents a new record for Croatia, which is not surprising as this species is recorded from neighbouring Hungary and Serbia, and has also been recorded from Albania, French mainland, Italian mainland, North Macedonia, Romania, and Ukraine (Pape 2004). Most species were found in natural and semi-natural habitats, although some of the species recorded in this study, i.e., S.  (Ren et al. 2018). All these five species were recorded in this study (Table 2). Sarcophaga (Pad.) similis was recorded in four localities (Darda, Petlovac, Popovac, Zmajevac).  (Table 2). In this study, a large number of flesh fly specimens were collected on or nearby pet animal faeces and on discarded leftover food. This is not surprising since it is known that S. (Pas.) albiceps, S. (Thy.) incisilobata, and Ravinia pernix visit excrements from humans and (other) animals (Papp 1992a(Papp , 1992b. Several species of flesh flies are also known to visit different animal carcasses (Szpila et al. 2015). Among them, the following species were recorded during this study: R. pernix, S. ) incisilobata were also collected in this study. Eighty years ago, Baranov (1940) confirmed the presence of five flesh fly species in a laystall in the village of Metajna on the Island of Pag, four of which were also recorded in this study.

Sarcophaga (Sarcophaga) croatica
In a similar study from the Polish Baltic coast, a number of species were recorded from a marshy habitat (15) and a sandy habitat (24)  lehmanni were also collected in this study. The large differences in the number of recorded species between Zmajevac and other localities may be explained by the much higher number of samples. This is clearly shown by the fact that in 2021 only 15 species were collected at the Zmajevac locality compared to the total number of 35 species that were sampled during all three years (2019-2021) at this locality. The lower number of recorded species at the Bilje locality was influenced by environmental factors such as open sun throughout the day (with afternoon temperatures ≥ 32 °C) and a lack of animal faeces and remains for food, which reduced the number of recorded species. The seven localities around pond habitats are polluted by different organic contaminations caused by various human activities, which can attract certain species for feeding and breeding.

Conclusions
The