Historical review of arachnological studies in Bulgaria
The arachnological studies in Bulgaria started at the end of the 19th century. The first data on spiders can be found in the works of Pavessi (1876) and Hristovich (1892). However, the numerous contributions of Drensky to the study of spiders and mites are considered as the beginning of regular and continuous arachnological research. His main contributions were written before the Second World War (Drensky, 1909, 1910, 1911a, b, 1912, 1913, 1915a, b, 1921, 1924, 1925, 1926, 1927a, b, 1929, 1930, 1931a, b, c, 1932, 1933, 1934a, b, c, 1936a, b, c, 1937, 1938a, b, 1939a, b, 1940a, b, 1942a, b, 1943, 1952, 1953, 1955, 1966). His book ‘Catalogue on Spiders of the Balkan Peninsula’ is the only catalogue published so far (Drensky, 1936a). There he reported 624 spider species found on the territory of Bulgaria. After the end of the War Drensky did not continue his intensive arachnological research and his last study on spiders in the South Dobrudzha was published in 1955.
In the 10 years which follows the arachnological research almost ceased until 1967 when new data on Bulgarian araneofauna appeared as a result of the regular research started by Deltshev. Biospeleological research in Bulgaria was intensified as well. Over 600 caves were studied and 76 spider species were established of which 1 genus and 9 species newly discovered (Deltshev, 1972d, 1973b, 1974, 1975a, 1977a, b, 1978a, 1980b). Data on the spatial distribution of spiders in cave biotopes and on the coenological relationships between species was presented as well (Deltshev, 1972a, b, c, 1973b, c, 1975a, b, 1982, 1983a, 1988c). The role of spiders in some pasture ecosystems in Bulgaria and Poland was studied (Deltshev & Kayak, 1974). The ecological research was continued by Blagoev. He studied the ecology of lycosid spiders (Blagoev & Deltshev, 1989; Deltshev & Blagoev, 1994, 1995).
The research efforts of some scientists were directed towards revision of old collections and their results were published as critical surveys of different genera and families (Deltshev, 1973c, 1980b, 1983c, d, 1987a, c, 1988c, 1990, 1993; Deltshev & Blagoev; 1995; Knoflach, 1999). Some of these data was published together with Dutch and Austrian arachnologists (van Helsdingen et al., 1977; Thaler et al., 1994; van Helsdingen et al., 2001).
Comprehensive research on the araneofauna of the following Bulgarian Mountains have been carried out so far: Rila (Drensky, 1932; Deltshev, 1995b, 2000a), Pirin (Drensky, 1921; Deltshev, 1983d, 1985, 1988a, b, 1990b, 1992b; Deltshev & Blagoev, 1997), Central Balkan (Drensky, 1911a; Deltshev, 1998, 2000b; Popov et al., 2000), Vitosha (Deltshev, 1967, 1980c), Sredna Gora (Lazarov et al., 2001), Osogovo (Tzonev & Lazarov, 2001), Chepun (Dimitrov & Lazarov, 2002). The research helped the precise range differentiation of the rare, relict, endemic and endangered species with in view of their conservation and protection. Many of the data contributed to the development of the National Biodiversity Conservation Strategy and National Parks Management Plans (Deltshev et al., 1993, 1998a, 2000a, b; Popov et al., 2000a).
In recent years the development of a database of Bulgarian spiders has started. The database have been designed, organised and maintained by Blagoev (Blagoev & Georgiev, 2000a, b; Deltshev et al., 1998). The data collected was used in the preparation of ‘A critical check list of Bulgarian spiders (Araneae)’ (Deltshev & Blagoev, 2001) as well as in the newly presented Check List of Bulgarian Spiders.
Fifty eight newly discovered species group taxa in Bulgaria, described mainly by Bulgarian arachnologists, are currently regarded as valid. The first descriptions of spiders based on Bulgarian material were published by Drensky (1915). He described a total of 43 species of which 13 still regarded as valid. The rest of the newly described taxa are due to the research of: Deltshev — 25, Lazarov — 8, Dimitrov — 3, Dimitrov & Lazarov — 2, Lazarov & Naumova — 2, Bosmans — 1, van Helsdingen — 1, Deltshev & Dimitrov — 1, Deltshev & Li — 1 and Logunov — 1.
At present the group of professional Bulgarian arachnologists number six persons.