Terrestrial invertebrate fauna of Polish caves – a summary of 100 years of research

The year 2018 is particularly important in the history of zoological research in Poland. A hundred years ago, Kazimierz Demel published the first work concerning the terrestrial cave fauna of caves in the Ojców area. In this paper we present the extent of research on the terrestrial invertebrate fauna of Polish caves in the last 100 years. All accessible research papers that have been published during this period were analysed. Based on published literature, 593 species of terrestrial invertebrate were recorded in Polish caves. Additionally, detailed list of species of individual taxonomic groups was provided.


Introduction
The year 2018 is particularly important in the history of zoological research conducted in our country as it closes a period of 100 years of research on terrestrial invertebrates inhabiting the caves of Poland. A hundred years ago, Kazimierz Demel published the first groundbreaking work concerning the fauna of caves in the Ojców area. Although many works regarding Poland's cave fauna have been published in the last 100 years, it is still of marginal research interest to Polish zoologists, ecologists or general biologists. The aim of this paper is to present the entire range of research on the terrestrial invertebrate fauna of Polish caves in the last 100 years.

Materials and methods
All accessible research papers regarding the terrestrial invertebrate fauna of Polish caves that were published in the last 100 years were analysed in this article. These include the accessible papers published as monographs, original research papers, notes and conference materials. The results were presented here as a historical overview of the research, a list of references and a list of proven invertebrate species. The generic names have been provided regarding taxonomic indexes Fauna Europaea https://fauna-eu.org and World Spider Catalog https://wsc.nmbe.ch.

Historical overview of the research
The beginning of interest in the terrestrial fauna of Polish caves dates back to the first years of the 20 th century when Kazimierz Demel conducted his pioneer research in 1914. Unfortunately, the First World War prevented him from processing and issuing the results, which were actually published in 1918. Demel presented the fauna inhabiting eight caves of the Ojców area (southern part of Kraków-Częstochowa Upland), i.e. Jaskinia Koziarnia, Jaskinia Pustelnia, Jaskinia Biała, Jaskinia Złodziejska, Jaskinia Zbójecka, Jaskinia Łokietka, Jaskinia Ciemna and Jaskinia Jerzmanowska. Despite the period devoted to the research being relatively short (two and a half months), Demel collected a vast number of invertebrates, and in the presented results listed 30 species of invertebrates, 11 of which were described as cave forms, although they could be observed outside of caves (contemporarily named as troglophiles). In his works, Demel compared his results to the ones already presented by the cave fauna researchers from Germany, Belgium, France and Austria, giving attention to faunal similarities with other caves. In the papers of the above-mentioned author, one can find both: a list of species and data concerning cave environment observations, i.e. temperature, humidity, light coverage and access to degrading organic matter, which enabled the author to perform ecological analyses.
Based on the material compiled by Demel, Stach (1919) proved the presence of five species of springtails, including description of one species new to science, i.e. Mesachorutes ojcovensis. The author also compared the Polish springtail fauna to that of other European countries and confirmed Demel's assumptions that troglobionts are scarce in Polish caves. Furthermore, the data concerning springtail species found in Polish caves were summarised by Stach (1947Stach ( -1963. In the 1920s, Arndt (1921Arndt ( , 1923 published two papers based on his research in a few caves and mines (e.g. Złota Sztolnia) in Sudety Mountains. Nowadays most of these mines are located in the Czech Republic, while others, i.e. Niedźwiedzia Jama or Solna Jama, in Poland. Despite the research was conducted only from March to October 1920, Arndt proved the presence of 42 invertebrate species (including stygobiotic ones) and recognised the Schaefferia emucronata springtail as a troglobiont species. He noticed that the fauna of the Sudety Mountains lacks the species typical to the caves of Harz Mountains, Central Alps and Urals, i.e. blind beetles (Coleoptera), Orthoptera and Acari. In the second paper, Arndt (1923) supplemented the information on ecological groups and faunal genesis in the examined subterranean sites.
Other papers devoted to the cave-dwelling fauna of the Sudety Mountains were published by Pax and Maschke (1935) and Pax (1937). The object of the research was both terrestrial and aquatic fauna in the Rogóżka Cave. The research, which began in 1933, was focused not only on the cave fauna but also on the environmental conditions, i.e. the physical and chemical properties of the lake water, and the air temperature. Nowadays the Rogóżka Cave is the non-existed cave, in 1962 it was partly destroyed by mining in the crystalline limestones quarry, and next the entrance was covered by stones (Bieroński et al. 2009).
The Second World War delayed the faunal research in Polish caves for a few years. The first post-war researcher who was interested in cave-dwelling invertebrate fauna was Kazimierz Kowalski, who presented the results of his biological observations and the research project on the Tatra Mountains caves for the years 1951-1952 in the "Wierchy" annual. In 1955, he published a paper with the results of the above-mentioned research. During his research, he visited all known Tatra caves, but his main research interest was in six caves, i.e. Jaskinia Dziura Wyżnia, Jaskinia Zimna, Jaskinia Groby, Jaskinia Magurska, Jaskinia Lodowa and Jaskinia Dziura. His methodology included not only the faunal collection by means of Barber traps or direct search methods, but also microclimate analyses, i.e. light influence and air movement. Kowalski did not limit his research to the invertebrate fauna, as it included also bats. In his work, the characteristics of the research area and detailed descriptions of microclimate conditions can be found.
In the following decades, i.e. in the 60s and 70s of the 20 th century, Skalski presented exceptional research activity in the field of cave-dwelling fauna. He published his first work together with Wójcik (Skalski and Wójcik 1968), where they presented faunal genesis and microclimate characteristics of selected caves of the Częstochowa area. They proved the presence of six troglobiont species i.e. Mesachorutes ojcoviensis, Catops tristis infernus, Choleva lederiana gracilenta, Porrhomma egeria, Arrhopalites pygmeus, Onychiurus alborufescens and also determined the geographical distribution of these species.
The subsequent works by Skalski (1967Skalski ( , 1969 were dedicated to invertebrate fauna in the Tatra Mountains. In addition to the presented list of species, he also considered the relationship between the age of the cave and the number of troglobionts as an important factor influencing the species variety. Furthermore, he presented detailed information about the occurrence of Onychiurus armatus springtails in the Mylna and Czarna caves, Hypena obsitalis butterflies in the Mylna cave and Exephanes ischioxanthus hymenoptera in Szczelina Chochołowska. In 1973, Skalski published an extensive paper on the research and observations conducted in the years 1957-1970 in 19 caves of the Częstochowa Upland. Using a wide range of entomological methods (Barber traps, Tullgren funnels, entomological sieves and direct searches), he detected 83 species belonging to a few arthropod and molluscan orders. He extensively discussed ecological issues, also concerning trogloxenes, for example he paid special attention to describing the associations of arthropods living or resting on cave walls. The paper includes valuable data on reproduction, position and spread of individual species in the caves like characteristics of massive occurrence of Choleva lederiana gracilenta if there is high availability of food.
Apart from the above mentioned research published in the form of papers, presentations at Speleological Conferences, which have been taking place since 1965, give an update on the invertebrate cave fauna research. The first information can be found in the materials form 3 rd /4 th Speleological Conference (1971), where  presented overview of terrestrial and aquatic fauna, named all the known species and compared the knowledge from various Polish cave regions.
In his subsequent paper,  focused on known data of invertebrate fauna again. However, he put particular emphasis on dominant groups and tried to determine the reasons for underground sites colonisation. He emphasised the primary dominance of not only insects and springtails in the caves but also spiders, and analysed the conditions favourable to cave organisms, i.e. food accessibility and cave habitat as a shelter for fauna during the winter.
In 1975, Baranek and Powichrowski published an article about the cave fauna in Dolina Wodącej. Three caves of the valley, Jaskinia Źródlana (Psia), Jasknia Zegarowa and Jaskinia Mroczna, were discussed in the paper. The authors observed the associations of arthropods trogloxenes like numerous fly community, spiders (particularly Meta sp.) and other arachnids on the cave walls. Springtails and beetles of families Staphylinidae and Catopidae (Leiodidae) were recognised among the regular cave-dwelling species. The only troglobiont species recorded was Porhomma moravicum (currently P. egeria), which was observed in Jaskinia Mroczna.
Sanocka-Wołoszynowa (1981) on Kraków -Częstochowa Upland arachnids study added great value to the state of knowledge of invertebrate fauna exploration. The author examined 184 caves and shelters; 40 of them were examined in all four seasons. Samples were collected by means of Barber traps or direct search. As a result, 13000 specimens representing 186 species of spiders, arachnids and pseudoscorpions were collected. Two species of spiders recorded deserve special attention: troglobiontic Porhomma egeria (in the paper P. moravicum) and troglophilic Meta menardi. Among arachnids also harvestman Ischyropsalis helwigii, known earlier from the Sudety Mountains area, the observation of which in Kraków -Częstochowa Upland widened the range of its occurrence. The author in addition to the detailed list of species, carried out an ecological and zoocoenological analysis, for example, she distinguished communities of arachnids living in the litter, associations of wall arachnids and a deep-cave group of species with dominant species Porrhomma egeria.
At the 15 th Speleological Conference, Sobiepanek (1985) described the results of the research conducted during Tatra Mountains caves inventory. During the research, the samples were collected by direct search or by means of Barber traps. As a result, many taxa belonging to dipterans, beetles, trichopterans, millipedes, spiders, gastropods, springtails and earthworms were observed. During the 30 th Speleological Conference, Gubała (1996) presented his paper about the results of an inventory of 131 caves and shelters in świętokrzyskie region.
Further papers were published after the year 2000. The studies by Maślak and Barczyk (2011) and Barczyk and Madej (2014) were devoted to cave mites. The first article refers to Oribatida dwelling in five Jurassic caves, i.e. Jaskinia Nietoperzowa, Jaskinia Wierna, Jaskinia Studnisko, Jaskinia Błotna and Jaskinia Pod Porzeczką, and their immediate surroundings. The study presented an analysis of faunistic similarities between the species and caves. Altogether 65 Orbatida species, including one typically cave dwelling species, were recorded. It was proven that the faunal composition of larger caves significantly differs from smaller ones. Communities of small caves, such as Jaskinia Błotna, Jaskinia Pod Porzeczką were similar to soil fauna communities. The species composition was mainly influenced by the accessibility of particular food sources (leaves, guano, wood) (Maślak and Barczyk 2011). The second paper refers to eight caves of the Kraków -Częstochowa Upland (Jaskinia Lodowa, Jaskinia poniżej Lodowej, Jaskinia Pod Porzeczką, Jaskinia Studnisko, Jaskinia Pod Sokołą, Jaskinia Jasna, Jaskinia Błotna and Jaskinia Schronisko koło Jaskini Lodowej), where 316 samples were collected. There were 270 samples collected from the immediate surroundings of the caves. As a result, the author identified 106 species from 13 families, including four species new in Polish fauna i.e. Paragamasus arcuatus, Parasitus hortivagus, Pachylaelaps sublongisetis, Pachyglobolaelaps hallidayi and troglobiont species recognised earlier in other caves. Significant differences in species composition between Acari communities inhabiting caves and cave surroundings were described.
Among the contemporary studies devoted to invertebrate fauna, Dumnicka and Płotek (2013) discussed the differences in invertebrate fauna between the caves Jaskinia Towarna and Jaskinia Dzwonnica, with regards to microclimate conditions, organic matter content in the cave deposits and tourism intensity.
During the 49 th Speleological Conference, Kocot -Zalewska (2015) presented the preliminary results of the research on Jaskinia Kroczycka fauna. The presentation included general data however indicated seven orders: butterflies, dipterans, spiders, beetles, trichopterans, mites and springtails. At the next Speleological Conference, Kocot -Zalewska (2016) presented the results of the observation of Jaskinia Towarna colonisation by Speonomus normandi hydrophilus of Leiodidae family. The beetle was introduced in the caves in 1982 and its natural place of occurrence is Arize Massif in Pyrenees.
In a contemporary paper, Kur et al. (2016) characterised the fauna of Jaskinia Szeptunów (Szmaragdowa). Based on the samples collected in the years 2005,2006,2010,2014,2015, 5 species of springtails, 2 species of Myriapoda, 1 spider species, 2 species of butterflies and mites were observed. The cave was opened in 1990 and the colonisation rate by living organisms was monitored.
At the 51 st Speleological Conference, Kocot -Zalewska and Słupińska (2017) presented the discovery of a great population of Choleva lederiana gracilenta, which is endemic to Sokole Mountain caves, and presented detailed information about its quantity, sex ratio and cave positioning. During the same Speleological Conference, Dumnicka (2017) discussed the state of knowledge of invertebrate cave fauna of Polish Tatra Mountains based on literature data, mainly the works by Stach (1934Stach ( , 1954 and Kowalski (1955).
Several short articles were devoted to interesting discoveries of invertebrate species found in caves (Dylewska and Błoszyk 2006, Kocot-Zalewska and Rozwałka 2018, Kasprzak 1973, Weiner 1990), however, several synthetic articles were also written, summarizing the state of knowledge and valorization of a valuable studied area (Błoszyk and Rozwałka 2008.

Checklist of terrestrial invertebrate record in Polish caves
Based on published literature, 593 species of terrestrial invertebrate are recorded in Polish caves.

Summary
Based on presented data, it can be noticed that researchers' interest in terrestrial invertebrate fauna, both historically and contemporarily, is relatively low in Poland. In the span of 100 years, just over 50 published papers have been focused on the terrestrial invertebrate fauna of Polish caves although the presence of 593 species has been reported. Such a low interest could be caused by the conviction that it is not worth involving in the research of fauna that lacks spectacular troglobionts. Once the fauna of Polish caves gains greater interest of academics from various groups, we will learn more about this most mysterious world.