Research Article
Research Article
Vertical distribution of spiders (Araneae) in Central European shallow subterranean habitats
expand article infoMilan Řezáč, Vlastimil Růžička§, Jan Dolanský|, Petr Dolejš
‡ Crop Research Institute, Praha, Czech Republic
§ Biology Centre, Czech Academy of Sciences, Institute of Entomology, České Budějovice, Czech Republic
| The East Bohemian Museum, Pardubice, Czech Republic
¶ Natural History Museum, Praha, Czech Republic
Open Access


Shallow subterranean habitats are among the last habitats in Central Europe to be arachnologically researched. Using stratified pipe traps, we studied the vertical distribution of spiders in soil and interspaces in bedrock (shallow subterranean habitats). Specifically, we sampled fauna in different substrates, including limestone, sandy marlstone, sandy marl, claystone, loess, and artificial gravel accumulation. Employing stratified pipe traps allowed us to identify the depth at which particular species occurred. Across multiple years and sampling sites, we collected 76 spider species, 21 of which showed an affinity for subterranean microhabitats. Some of these species occurred in interspaces in soil and bedrock, whereas others have been previously found in subterranean ant nests and animal burrows. We collected five species (Iberina microphthalma, Centromerus cf. piccolo, Porrhomma cambridgei, P. microcavense, and P. microps) almost exclusively at depths over half a meter, suggesting the strong affinity of these species for a subterranean lifestyle. We provide diagrams of these species’ vertical distribution and photo-document eye reduction. Our study demonstrates that poorly studied shallow subterranean habitats harbor diverse subterranean spider fauna, including several previously considered rare species in Central Europe.


Araneae, Centromerus, Czechia, edaphomorphism, Iberina, micropthalmic spiders, Palliduphantes, pipe traps, Porrhomma, soil spiders, troglomorphism


Subterranean habitats range from large spaces in caves to tiny spaces such as fissure networks in bedrock or soil pores (Culver and Pipan 2014). They are typically characterized by the absence of light, almost 100% relative air humidity, and small temperature fluctuations over a year (Badino 2010). Animals fully adapted to subterranean habitats, e.g., those demonstrating depigmentation, reduced eyes, and other so-called troglomorphic traits, are sometimes caught by pitfall traps also on the surface but usually as singletons and only during the humid and cold season (Czech Arachnological Society 2022). Some subterranean habitats in central Europe are already well-studied from an arachnological point of view, especially caves or scree slopes (Růžička et al. 1995; Růžička et al. 2012). Caves and scree slopes provide relatively large spaces and thus can be inhabited by troglomorphic spiders like Bathyphantes eumenis buchari Růžička, 1988 (Růžička 1988) and Meta menardi (Latreille, 1804) (Mammola and Isaia 2014). In contrast, the arachnofauna of shallow subterranean habitats within coarse substrata, which are difficult to access, is poorly studied (Mammola et al. 2016). Shallow subterranean habitats are areas of habitable space that are less than 10 m in depth from the surface. These range from large areas such as shallow caves and lava tubes, to tiny areas such as cracks in ceilings, or spaces in soil (Culver and Pipan 2014). Different authors have used perforated pipe traps with one cup on the bottom to sample invertebrates in shallow subterranean habitats and deep soil strata (e.g., López and Oromí 2010; Deltshev et al. 2011; Jiménez-Valverde et al. 2015; Mammola et al. 2017; Ledesma et al. 2020). Conversely, Schlick-Steiner and Steiner (2000) constructed a trap consisting of a perforated pipe and a set of removable plastic cups situated on a central metal axis. The cups collect animals entering the pipe through holes at different depths, allowing to study the vertical distribution of arthropods in shallow subterranean habitats. For example, this trap design has been used to study the vertical distribution of spiders in soil and fissured rock (Laška et al. 2011; Růžička and Dolanský 2016), and springtails (Rendoš et al. 2016; Jureková et al. 2021), and myriapods (Haľková et al. 2020) in forested scree slopes.

In this study, we employed stratified pipe traps to explore spider fauna in soils, gravel, and loess (up to two meters in depth) on bedrock known to harbor fissure networks. The study aimed to describe the vertical distribution of spiders in these unique subterranean ecosystems and to describe species’ preferences for certain types of substrates (microhabitats).

Materials and methods

Study sites

The research was carried out at ten sites in Czechia (Table 1, Fig. 1). In one site, Suchomasty, we documented temperature fluctuations measured by dataloggers Tinytag Ultra2 every three hours at the maximum sampling depth and on the surface (Fig. 5).

Figure 1. 

Locations of the study sites in Czechia. 1 – Kostelní Bříza, 2 – Raná, 3 – Suchomasty, 4 – Nebušice, 5 – Ctiněves, 6 – Hostovice, 7 – Mravín, 8 – Pouzdřany, 9 – Dolní Věstonice, 10 – Kurovice. For details, see Table 1.

Table 1.

Characteristics of the study sites. n – number of pipe traps.

Site Coordinates Altitude [m a.s.l.]/average annual temperature n/pipe length Years Substrate Vegetation
Kostelní Bříza 50.1119°N, 12.6349°E 570/7 °C 2/110 and 80 cm 2017–2021 gravel accumulation from a metal mine sparse Pinus sylvestris and Betula pendula wood
Raná 50.4067°N, 13.7450°E 250/9 °C 1/110 cm 2014–2016 stony rendzina soil and fissure network in sandy marlstone steppe grassland
Suchomasty 49.9062°N, 14.0667°E 405/8 °C 3/200 cm 2015–2020 Stony brown soil on limestone bedrock Carpinion forest
Nebušice 50.1019°N, 14.3050°E 350/9 °C 1/110 cm 2017–2021 stony brown soil and fissure network in sandy marlstone (Fig. 2B) Carpinion forest
Ctiněves 50.3707°N, 14.3180°E 265/9°C 2/120 cm 2019–2021 thin ranker soil on sandy gravel planted Robinia wood
Hostovice 50.0093°N, 15.8509°E 230/9°C 1/130 cm 2015–2018 Stony scree soil on claystone bedrock (Fig. 2C) deciduous bush
Mravín 49.9445°N, 16.0516°E 315/9°C 2/120 cm 2013–2021 thin rendzina soil on sandy marl oak forest
Pouzdřany 48.9429°N, 16.6430°E 290/10 °C 2/90 cm 2017–2021 Thin rendzina on loess steppe grassland
Dolní Věstonice 48.8856°N, 16.6562°E 205/10 °C 1/90 cm 2019–2022 bare loess deciduous bush
Kurovice 49.2736°N, 17.5249°E 305/9°C 2/100 cm 2013–2021 Thin brown soil on limestone bedrock Carpinion forest


The plastic pipes (for lengths see Table 1) had an inner diameter of 7 cm and were perforated by oblique, 5 mm wide cuts. Plastic cups were mounted onto a threaded metal rod at 10 cm distances (for example, a 2-m long pipe contained 20 cups) (Fig. 2A) and contained a solution of 6% formaldehyde with few drops of detergent (for more details see Růžička and Dolanský 2016). We installed these traps in excavated holes or boreholes (a drilling machine was used in Suchomasty) and emptied them once a year. When we installed multiple pipes per site, each pipe was buried in a separate hole. Since traps were buried for long periods (between 2 and 8 years depending on the site), we expect the initial mixing of the soil layers to exert a minor role in the distribution of fauna.

Figure 2. 

A a set of plastic cups taken from the pipe trap in the Carpinus forest on limestone near Suchomasty (photo M. Šafra); the soil profile is inhabited by Porrhomma cambridgei, see Fig. 3A B a fissure network in sandy marl near Nebušice, which was rich in Porrhomma microcavense, see Fig. 3D (the pipe trap was ten meters from this quarry wall) (photo M. Řezáč) C, D a scree soil near Hostovice, which was rich in Porrhomma microps, see Fig. 3E (photo J. Dolanský) E a fissure network in sandy marl near Mravín (the pipe trap was 200 meters from this profile) (photo J. Dolanský) F a hole for a pipe trap near Mravín in the soil, which was rich in Iberina microphthalma and P. cambridgei, see Fig. 3C (photo J. Dolanský).

Spider identification

Spiders were sorted and examined under an Olympus SZX12 stereomicroscope in 80% ethanol. Spider identification follows Nentwig et al. (2022), and nomenclature is in accordance with the World Spider Catalog (2022). The individuals were deposited at the institutions of the authors. Photographs were taken with an Olympus C-5060 wide-zoom digital camera mounted on an Olympus BX40 microscope. The images were processed using CombineZP image stacking software.

Relation to subterranean habitats

We classified the affinity of particular species to subterranean environments according to their vertical distribution. Further, we considered (1) morphological adaptations for subterranean life, (2) habitat, where they were found so far, (3) pattern of their distribution (common or rare on the surface habitats), (4) what environment they need for their lifestyle (see column “relation to the subterranean habitat – RSH” in Table 2). Morphological features, in particular depigmentation and a reduction in eye size, were recorded during identification, and the carapace size data were taken from the literature (Merrett et al. 1993; Weiss 1996; Růžička 2018, 2022; Šestáková et al. 2018; Nentwig et al. 2022). Data on spider occurrence in Czechia, habitat, and natural history were taken from a database of records of spiders in Czechia (Czech Arachnological Society 2022) and Buchar and Růžička (2002). The following categories were distinguished:

Table 2.

Vertical distribution of the collected spider species sorted according to the average depth from the deepest point toward the surface. Depth: mean ± SEM (95% confidence interval). The species that were significantly more common in deep subterranean habitats than close to the surface are shown in bold. n – number of specimens captured. Sites: Bří – Kostelní Bříza, Cti – Ctiněves, Hos – Hostovice, Kur – Kurovice, Mra – Mravín, Neb – Nebušice, Pou – Pouzdřany, Ran – Raná, Such – Suchomasty, Věs – Dolní Věstonice. RSH – relation to the subterranean habitat: 1 – surface species; 2 – detritus layer species (B – with burrows in the soil, H – requiring high air humidity); 3 – soil species (below the detritus layer, but found relatively often on the soil surface, A – ant nest species); 4 – soil-bedrock species (basal layers of the soil, very rarely found on the soil surface).

Species Family Depth [cm] n Geology Site RSH
Porrhomma cambridgei Merrett, 1994 Linyphiidae 100 ± 5.9 (89–112) 45 sandy marl, limestone Mra, Such 4
Porrhomma microps (Roewer, 1931) Linyphiidae 93 ± 2.0 (89–97) 156 sandy marl, limestone, claystone Hos, Kur, Mra, Such 4
Porrhomma microcavense Wunderlich, 1990 Linyphiidae 86 ± 3.3 (80–93) 24 sandy marlstone Neb 4
Mastigusa arietina (Thorell, 1871) Dictynidae 80 ± 21.2 (38–122) 2 sandy marl, gravel heap Bří, Mra 3A
Iberina microphthalma (Snazell & Duffey, 1980) Hahniidae 78 ± 3.7 (70–85) 25 sandy marl Mra 4
Centromerus cf. piccolo Weiss, 1996 Linyphiidae 75 ± 3.5 (68–82) 17 loess Pou, Věs 4
Porrhomma campbelli F. O. Pickard-Cambridge, 1894 Linyphiidae 69 ± 2.3 (65–74) 12 gravel heap Bří 2
Pseudomaro aenigmaticus Denis, 1966 Linyphiidae 65 ± 31.8 (3–127) 2 gravel heap Bří 4
Walckenaeria capito (Westring, 1861) Linyphiidae 63 ± 8.0 (47–78) 8 sandy marlstone, gravel heap Bří, Ran 2
Mioxena blanda (Simon, 1884) Linyphiidae 60 ± 23.0 (15–105) 3 sandy marl and marlstone, gravel Cti, Mra, Ran 3
Nesticus cellulanus (Clerck, 1757) Nesticidae 50 ± 0 (50) 1 claystone Hos 4
Robertus neglectus (O. Pickard-Cambridge, 1871) Theridiidae 50 ± 11.5 (27–73) 3 limestone Such 2
Porrhomma microphthalmum (O. Pickard-Cambridge, 1871) Linyphiidae 43 ± 9.0 (26–61) 3 sandy marl, limestone, claystone Hos, Mra, Such 3
Cicurina cicur (Fabricius, 1793) Dictynidae 42 ± 1.5 (39–45) 285 loess, sandy marl, marlstone, limestone, claystone, gravel heap Bří, Hos, Kur, Mra, Neb, Ran, Such, Věs 3
Harpactea lepida (C. L. Koch, 1838) Dysderidae 40 ± 5.4 (29–51) 7 limestone, gravel heap Bří, Such 2H
Centromerus cavernarum (L. Koch, 1872) Linyphiidae 40 ± 14.1 (12–68) 2 gravel heap Bří 3
Jacksonella falconeri (Jackson, 1908) Linyphiidae 40 ± 0 (40) 1 gravel heap Bří 4
Coelotes terrestris (Wider, 1834) Agelenidae 40 ± 0 (40) 1 sandy marl Mra 2B
Micrargus herbigradus (Blackwall, 1854) Linyphiidae 39 ± 3.8 (31–46) 25 sandy marl and marlstone, limestone, gravel heap Bří, Kur, Mra, Neb 2
Palliduphantes insignis (O. Pickard-Cambridge, 1913) Linyphiidae 35 ± 4.0 (27–43) 31 loess Pou, Věs 4
Syedra myrmicarum (Kulczyński, 1882) Linyphiidae 35 ± 3.5 (28–42) 2 sandy marl Mra 3A
Palliduphantes alutacius (Simon, 1884) Linyphiidae 34 ± 2.2 (30–38) 83 loess, sandy marl, claystone, limestone Hos, Kur, Mra, Věs 3
Palliduphantes pallidus (O. Pickard-Cambridge, 1871) Linyphiidae 33 ± 3.9 (26–41) 35 sandy marlstone, gravel heap Bří, Neb, Ran 3
Centromerus cf. minutissimus Merrett & Powel, 1993 Linyphiidae 30 ± 0 (30) 1 gravel heap Bří 4
Metopobactrus prominulus (O. Pickard-Cambridge, 1873) Linyphiidae 30 ± 0 (30) 1 gravel heap Bří 2
Walckenaeria dysderoides (Wider, 1834) Linyphiidae 30 ± 6.2 (18–42) 8 loess, limestone Kur, Such, Věs 2
Walckenaeria obtusa Blackwall, 1836 Linyphiidae 30 ± 0 (30) 1 limestone Kur 2
Robertus arundineti (O. Pickard-Cambridge, 1871) Theridiidae 30 ± 0 (30) 1 limestone Such 2
Piratula uliginosa (Thorell, 1856) Lycosidae 30 ± 7.1 (16–44) 2 gravel heap Bří 1
Clubiona terrestris Westring, 1851 Clubionidae 30 ± 7.1 (16–44) 2 sandy marl, claystone Hos, Mra 1
Robertus lividus (Blackwall, 1836) Theridiidae 26 ± 3.2 (19–32) 18 loess, limestone Kur, Pou, Věs 2
Agyneta rurestris (C. L. Koch, 1836) Linyphiidae 25 ± 3.5 (18–32) 2 limestone, gravel heap Bří, Such 1
Histopona torpida (C. L. Koch, 1837) Agelenidae 25 ± 10.6 (4–46) 2 sandy marl Mra 2H
Hahnia pusilla C. L. Koch, 1841 Hahniidae 24 ± 2.1 (20–28) 16 sandy marl, limestone, gravel heap Bří, Kur, Mra 2
Harpactea rubicunda (C. L. Koch, 1838) Dysderidae 23 ± 2.7 (18–29) 6 sandy marl and marlstone, limestone Mra, Neb, Such 2
Theonoe minutissima (O. Pickard-Cambridge, 1879) Theridiidae 23 ± 2.7 (18–29) 6 gravel heap Bří 4
Dysdera cechica Řezáč, 2018 Dysderidae 23 ± 3.7 (16–30) 10 loess, limestone Kur, Pou, Věs 2
Diplostyla concolor (Wider, 1834) Linyphiidae 22 ± 1.4 (20–25) 102 claystone, sandy marlstone, limestone Hos, Kur, Neb, Ran 2
Dysdera erythrina (Walckenaer, 1802) Dysderidae 20 ± 2.2 (16–24) 11 limestone, gravel heap Bří, Such 2
Episinus truncatus Latreille, 1809 Theridiidae 20 ± 7.7 (5–35) 3 loess Pou 1
Mermessus trilobatus (Emerton, 1882) Linyphiidae 20 ± 0 (20) 1 claystone Hos 1
Tapinocyba insecta (L. Koch, 1869) Linyphiidae 20 ± 0 (20) 1 gravel Cti 2
Tapinocyboides pygmaeus (Menge, 1869) Linyphiidae 20 ± 0 (20) 1 gravel heap Bří 3
Amaurobius jugorum L. Koch, 1868 Amaurobiidae 20 ± 0 (20) 1 sandy marl Mra 2B
Trochosa ruricola (De Geer, 1778) Lycosidae 20 ± 7.7 (5–35) 3 sandy marlstone Ran 2B
Phrurolithus festivus (C. L. Koch, 1835) Phrurolithidae 18 ± 1.7 (15–22) 31 loess, sandy marl and marlstone, limestone, gravel heap, gravel Bří, Cti, Mra, Neb, Ran, Such, Věs 1
Centromerus sylvaticus (Blackwall, 1841) Linyphiidae 17 ± 1.8 (13–20) 13 loess, limestone, sandy marlstone, gravel heap Bří, Neb, Ran, Such, Věs 2
Trachyzelotes pedestris (C. L. Koch, 1837) Gnaphosidae 17 ± 1.2 (14–19) 18 loess, sandy marlstone, limestone, gravel Cti, Kur, Ran, Věs 1
Inermocoelotes inermis (L. Koch, 1855) Agelenidae 16 ± 3.2 (10–22) 5 limestone, gravel heap Bří, Kur 2B
Haplodrassus silvestris (Blackwall, 1833) Gnaphosidae 15 ± 3.5 (8–22) 2 limestone Kur 1
Centromerus serratus (O. Pickard-Cambridge, 1875) Linyphiidae 14 ± 2.1 (10–18) 5 sandy marl Mra 3
Agroeca cuprea Menge, 1873 Liocranidae 13 ± 1.4 (8–32) 3 sandy marlstone, loess Pou, Ran 1
Apostenus fuscus Westring, 1851 Liocranidae 13 ± 0.7 (11–14) 31 limestone Kur 1
Tenuiphantes flavipes (Blackwall, 1854) Linyphiidae 11 ± 0.5 (10–12) 11 loess, limestone Kur, Such, Věs 1
Euryopis flavomaculata (C. L. Koch, 1836) Theridiidae 10 ± 0 (10) 2 limestone Kur 2
Agyneta saxatilis (Blackwall, 1844) Linyphiidae 10 ± 0 (10) 1 loess Pou 1
Linyphia hortensis Sundevall, 1830 Linyphiidae 10 ± 0 (10) 1 sandy marl Mra 1
Micrargus subaequalis (Westring, 1851) Linyphiidae 10 ± 0 (10) 1 sandy marlstone Ran 2
Oedothorax retusus (Westring, 1851) Linyphiidae 10 ± 0 (10) 1 limestone Kur 2
Pelecopsis radicicola (L. Koch, 1872) Linyphiidae 10 ± 0 (10) 1 gravel heap Bří 2
Aulonia albimana (Walckenaer, 1805) Lycosidae 10 ± 0 (10) 1 limestone Kur 2B
Pardosa lugubris (Walckenaer, 1802) Lycosidae 10 ± 0 (10) 45 sandy marlstone, limestone Kur, Neb 1
Pardosa riparia (C. L. Koch, 1833) Lycosidae 10 ± 0 (10) 5 sandy marlstone Ran 1
Trochosa terricola Thorell, 1856 Lycosidae 10 ± 0 (10) 2 limestone Such 2B
Zora spinimana (Sundevall, 1833) Miturgidae 10 ± 0 (10) 1 limestone Kur 1
Agroeca brunnea (Blackwall, 1833) Liocranidae 10 ± 0 (10) 1 limestone Kur 1
Phrurolithus pullatus (C. L. Koch, 1835) Phrurolithidae 10 ± 0 (10) 1 loess Pou 1
Zodarion germanicum (C. L. Koch, 1837) Zodariidae 10 ± 0 (10) 5 limestone Kur 1
Drassyllus praeficus (L. Koch, 1866) Gnaphosidae 10 ± 0 (10) 1 loess Pou 1
Drassyllus pumilus (C. L. Koch, 1839) Gnaphosidae 10 ± 0 (10) 4 loess Pou 1
Haplodrassus umbratilis (L. Koch, 1866) Gnaphosidae 10 ± 0 (10) 3 gravel heap Bří 1
Zelotes apricorum (L. Koch, 1876) Gnaphosidae 10 ± 0 (10) 8 limestone Kur 1
Ozyptila praticola (C. L. Koch, 1837) Thomisidae 10 ± 0 (10) 1 limestone Kur 1
Ozyptila trux (Blackwall, 1846) Thomisidae 10 ± 0 (10) 1 loess Pou 1
Xysticus luctator L. Koch, 1870 Thomisidae 10 ± 0 (10) 1 limestone Kur 1
Euophrys frontalis (Walckenaer, 1802) Salticidae 10 ± 0 (10) 2 limestone Kur 1
  1. surface species occur only at the surface, on the ground, or in the vegetation. Their presence underground is accidental; they possess eyes of normal size and are normally pigmented.
  2. detritus layer species live in detritus on the soil surface. They are rare in deeper soil layers. They possess eyes of normal size and are normally pigmented. Two special cases are within this category:
  1. species with burrows in soil spend at least part of their lives in shallow burrows in soil; they possess eyes of normal size and are normally pigmented.
  2. species requiring high air humidity require habitats with constantly high air humidity, regardless of whether the habitats are superficial or subterranean; they possess eyes of normal size and are normally pigmented.
  1. soil species are more common deeper in humus soil than in detritus, but they appear on the soil surface relatively often; they are usually tiny and less pigmented, and their eyes are relatively smaller than those of their relatives. A special case is within this category:
  1. soil ant nest species spend the majority of their lives in ant nests in the soil; they are less pigmented, and their eyes are relatively smaller than those of their surface relatives.
  1. soil-bedrock species live in the basal mineral layers of soil on eroded bedrock surfaces (or in other spacious subterranean habitats) and appear on the soil surface very rarely; they are pale, and their eyes are significantly reduced; they can be larger with relatively long legs.

Data analyses

We used descriptive statistics [mean, standard error (SEM), and 95% confidence interval] to assess the species’ preference for surface versus subterranean habitats, approximated via the depth of capture of each individual. In cases where the whole confidence interval was below a depth of 20 cm (the depth of the two uppermost cups in the trap, where the surface species can easily enter), we assumed the species to be more common below 20 cm depth than above it (the species shown in bold in Table 2). Data were handled in R, version 3.6.2 (R Core Team 2019).


We captured 1179 adult spider specimens belonging to 76 species. In total, 17 species were found to be more common under the surface than on the surface (shown in bold in Table 2); singletons were not evaluated, but they are included in Table 2. Five species occurred preferentially below 70 cm (more than 15 specimens, Fig. 3). These were Porrhomma cambridgei, Porrhomma microps, Porrhomma microcavense, Iberina microphthalma, and Centromerus cf. piccolo. They possessed remarkably reduced eyes (Fig. 4). We called them “soil-bedrock species”, as they probably occur in the interface between the soil and bedrock. In addition to these five species, we also considered Pseudomaro aenigmaticus, Nesticus cellulanus, Jacksonella falconeri, Palliduphantes insignis, Centromerus cf. minutissimus and Theonoe minutissima as belonging to this category. We further considered eight species to represent soil species (see the chapter Relation to subterranean habitats in MM for definitions of these categories: Mioxena blanda, Porrhomma microphthalmum, Cicurina cicur, Tapinocyboides pygmaeus, Centromerus cavernarum, Centromerus serratus, Palliduphantes alutacius, and Palliduphantes pallidus. We also recorded two myrmecophilous species occurring in ant nests in the soil, Mastigusa arietina, and Syedra myrmicarum. The remaining captured species were classified as detritus layer species (28) or as species with no relation to subterranean habitats (27).

Figure 3. 

Panels show soil profiles and the depth-dependent occurrence of microphthalmic spider species (depths in cm) A Suchomasty, soil on limestone B Věstonice, loess C Mravín, stony soil above sandy marl D Nebušice, stony soil, and fissure network in sandy marl E Hostovice, stony soil above claystone.

Figure 4. 

Carapaces of female spider species found deep in the Czech shallow subterranean habitats A Porrhomma microps from Hostovice B P. microcavense from Nebušice C P. cambridgei from Suchomasty D Iberina microphthalma from Mravín E Centromerus cf. piccolo from Dolní Věstonice. Scale bars: 0.1 mm (photos V. Růžička).

Figure 5. 

Temperature fluctuations in shallow subterranean habitats (below ground) were minor compared to temperature fluctuations on the surface (above ground). Data were collected from the study site at Suchomasty, between 23 April 2015 to 15 April 2017, taking one measurement every three hours. Above ground: 2.5 m above the ground, in shade. Below ground: at 2 m depth.


At least 21 species collected in our pipe traps exhibited morphological (eye reduction and depigmentation) and distributional (rare occurrence in surface habitats and regular presence in subterranean habitats) characteristics typical of subterranean fauna (categories 3 and 4 in Table 2). Of these, twelve species were more frequent below 20 cm than on the surface (marked bold in Table 2). The numbers of collected individuals in the remaining nine species were too low to demonstrate the same preference. On the other hand, five other species, Porrhomma campbelli, Walckenaeria capito, Robertus neglectus, Harpactea lepida, and Micrargus herbigradus, did not exhibit morphological or distributional features (they are common in surface habitats) characteristic of subterranean fauna but were more frequent below 20 cm than on the surface (also marked bold in Table 2). However, this result is based on low specimen numbers. The remaining species did not have any affinity for the subterranean environment; they usually occur on the soil surface or in detritus. These species probably crawled down the substrate along the pipe where the soil became loose due to digging. Such vertical migration could have happened during autumn and winter months when even the surface species search for suitable spots for overwintering.

The main subterranean spider groups

The captured subterranean species belonged to the families Linyphiidae, Hahniidae, Theridiidae, and Nesticidae, with Linyphiidae having the greatest abundance and species richness. Three genera dominate in the Central European shallow subterranean habitats: Centromerus, Palliduphantes, and especially Porrhomma. At two study sites, Mravín and Suchomasty, Porrhomma cambridgei and Porrhomma microps were found to occur syntopically. In both cases, the smaller P. cambridgei was found deeper than the larger P. microps (Fig. 3A, C). So far, Porrhomma campbelli has been known from the moss in wet habitats, such as peat bogs, spruce forests, and brook and pond margins (Růžička 2018). Here, we present the first finding of this species from subterranean habitats in Czechia.

The genus Centromerus was represented by four species, two of which, C. cf. piccolo and C. cf. minutissimus, were new to Czechia. We captured 17 specimens of Centromerus cf. piccolo at depths of 50–90 cm in loess accumulations in south Moravia. Previously, Centromerus piccolo had been known only from Germany (Weiss 1996; Nentwig et al. 2022). As the genitalic morphology of our specimens slightly differs from the illustrated type specimens of C. piccolo (Weiss 1996), we can not exclude the possibility that this is a closely related new species. In the artificial gravel accumulation in western Bohemia, we found two Centromerus females that are not described in the literature. Based on somatic characters (including small body size, eye reduction, and depigmentation) and the fact that the only Central European Centromerus species with unknown females was Centromerus minutissimus, which were known from England, Germany (the site in southern Saxony-Anhalt is only 200 km northwest of our site), south France and Spain (Merrett et al. 1993; Cárdenas and Barrientos 2011; Nentwig et al. 2022, GBIF –, INPN –, we preliminarily determined these individuals to be Centromerus cf. minutissimus.

We captured three species of the genus Palliduphantes. Palliduphantes insignis has been found in Czechia very rarely, only on the steppes on rocks or loess in warm areas (Buchar and Růžička 2002). We found 31 specimens at a depth of approximately 30 cm in loess. Thus, its preferred microhabitats are probably micro spaces in soil and fissures in bedrock. Palliduphantes pallidus and Palliduphantes alutacius sensu Miller and Obrtel (1975) are closely related taxa that are not morphologically clearly separated in Czechia. Instead, there are mainly typical Palliduphantes pallidus in the western part of Czechia, while in the eastern part typical Palliduphantes alutacius occurs, and morphologically intermediate forms can be found between. This pattern probably demonstrates the introgression of these two taxa in this territory. These species are among the most common subterranean species in Czechia and are also often found at the surface.

Concerning the remaining subterranean linyphiid spiders, we found four species of the subfamily Erigoninae: Jacksonella falconeri, Mioxena blanda, Pseudomaro aenigmaticus, and Tapinocyboides pygmaeus. Singletons of these species have rarely been found on the surface, usually in open xerothermic habitats (Czech Arachnological Society 2022). Our data show that the main microhabitats of these species are interspaces in various substrata.

The subterranean Hahniidae spiders were represented by three species. European records of Iberina microphthalma were summarized by Růžička and Dolanský (2016). Furthermore, in Czechia, this species was collected in the substratum on claystone, sandy marlstone, or sandy marl (Růžička 2022). We found 17 specimens in the soil on sandy marl at depths of 40–120 cm (Fig. 3C). Cicurina cicur is common under stones, in leaf litter, and decaying wood in forests, as well as in shallow subterranean habitats (Buchar and Růžička 2002; Růžička and Dolanský 2016). Because of its morphological appearance – depigmentation and small eyes – it is expected for this species to spend most of its life in the subterranean environment, especially in southern Europe (Mammola et al. 2022). Indeed, we found it to be dominant in the studied shallow subterranean habitats.

Nesticus cellulanus is the only representative of Nesticidae, the spiders mainly occurring in subterranean environments (Mammola et al. 2022). As this species is relatively large, it mainly occurs in caves, scree slopes, or man-made subterranean spaces, whereas it is rare in interspaces in the substratum.

The family Theridiidae was represented by Theonoe minutissima and some species of the genus Robertus. Theonoe minutissima regularly occurs in scree slopes, we found it only inside artificial gravel accumulation. Robertus species recorded during our study are common in detritus.

Myrmecophilous species

At two sites, Kostelní Bříza and Mravín, we captured the relatively large depigmented hahniid spider Mastigusa arietina, which is known to live in subterranean ant nests (Nentwig et al. 2022). At the Mravín site, it was found with another myrmecophilous spider, Syedra myrmicarum. The dominant co-occurring ant species was Lasius flavus (Fabricius, 1782).

Troglomorphism versus edaphomorphism

The body size and relative length of appendages of subterranean species may depend on the size of the spaces they inhabit (Pipan and Culver 2017). Predictably, an elongation of appendages is an adaptation to life in relatively large subterranean spaces, typically caves (troglomorphism, Zacharda 1979). In contrast, a diminished body size represents an adaptation to life in relatively small, narrow subterranean spaces, typically of soils (edaphomorphism, Zacharda 1979). Altogether, the species collected during this study cover the continuum from troglomorphic to edaphomorphic species. For example, relatively large, long-legged Porrhomma microps (carapace width 0.84 mm) and P. microcavense (carapace width 0.75 mm) represent typical troglomorphic species. They are characteristic of the interface between soil and sandy marlstone that harbors relatively large interspaces (Fig. 2B). Because of harsh climatic conditions during Quaternary glaciations, Central Europe lacks large troglomorphic spiders, known, for example, from Mediterranean caves (Culver et al. 2006). The most troglomorphic species of this region are still small enough to also occur in soil (Růžička 1999).

The edaphomorphic species collected during this study were tiny Centromerus (C. cf. piccolo and C. cf. minutissimus), Porrhomma cambridgei, Iberina microphthalma, and tiny Erigoninae linyphiids, all of which have carapace widths less than 0.6 mm. They probably live in narrow interspaces in soil or loess; however, they also occur in deep caves (Růžička and Buchar 2008; Růžička 2018, 2022).

Preferences for bedrock and climate

Different shallow subterranean habitats presumably provide microhabitats that are preferred by different species. Indeed, some subterranean species collected in the soil-bedrock interface seem to exhibit a preference for specific depths and substrates. For example, Centromerus cf. piccolo is characteristic of loess, and Porrhomma microcavense and Iberina microphthalma are characteristic of sandy marlstone. The species that occur in the surface layer of the soil seem not to express such preferences (for example, Centromerus serratus, C. cavernarum, Mioxena blanda, Palliduphantes spp., Porrhomma microphthalmum, P. microps, Tapinocyboides pygmaeus, Cicurina cicur).

The fauna of shallow subterranean habitats seems to be richer in warm areas than in cold ones. The species Centromerus cf. piccolo, Mioxena blanda, Palliduphantes insignis, Porrhomma cambridgei, and Iberina microphthalma are restricted to the warmest regions of Czechia. Additionally, vegetation can be expected to modify the temperature regime in the soil. A large number of the soil species found during this study live in substrates that occur in partly open xerothermic habitats (for example, Centromerus cf. piccolo, Palliduphantes insignis, Tapinocyboides pygmaeus, and Iberina microphthalma). On the other hand, some species live in habitats that maintain stable humidity and temperature, such as scree forests (e.g., Centromerus cavernarum, Porrhomma campbelli, Theonoe minutissima).


Interestingly, the only artificial habitat that was studied, an almost hundred-year-old gravel heap from a polymetallic ore mine near Kostelní Bříza, harbors relatively rich subterranean fauna. Several species with relatively small eyes, in particular Jacksonella falconeri, Pseudomaro aenigmaticus, Tapinocyboides pygmaeus, Centromerus cavernarum, Centromerus cf. minutissimus, Palliduphantes pallidus, Porrhomma campbelli, Theonoe minutissima, Cicurina cicur, and Mastigusa arietina were found here. Thus, at least these species are able to colonize new isolated sites, probably by ballooning, and they cannot be considered relics like the endemic fauna in limestone caves in the Mediterranean. For Pseudomaro aenigmaticus, this ability was confirmed by the capture of specimens in aeroplankton at 12 m height (Blick and Kreuels 2002).


Our study demonstrates that underexplored shallow subterranean habitats in Central Europe harbor rich subterranean spider fauna. Some of these species were considered very rare in the past. However, we came to the same conclusion as Polenec (1970): these species are, in fact, quite abundant in these hardly accessible and largely overlooked habitats.


We thank Stano Pekár for assistance with the statistical analysis, Nela Gloríková for help with the figures, and Stefano Mammola, Konrad Wiśniewski, and Julien Petillon for revising this manuscript. Milan Řezáč was supported by the Ministry of Agriculture of the Czech Republic (project MZe RO0418). Vlastimil Růžička was supported by the Institute of Entomology, Biology Centre, Czech Academy of Sciences, project RVO: 60077344. Research in Suchomasty was allowed and technically and financially supported by the company Velkolom Čertovy schody, a.s. (AP 10/33).


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