Corresponding author: Pallieter De Smedt (
Academic editor: S. Taiti
Woodlice are key organisms for nutrient cycling in many terrestrial ecosystems; however, knowledge on this invertebrate group is limited as for other soil fauna taxa. Here, we present an annotated checklist of the woodlice of Belgium, a small but densely populated country in Western Europe. We reviewed all 142 publications on Belgian woodlice, the oldest dating back to 1831 and re-identified all doubtful specimens from the Royal Belgian Institute of Natural Sciences (RBINS) collection. These data is complemented with observations from extensive field surveys dating from March 2014 until December 2017. We report 36 species of woodlice with free-living populations for Belgium. Nine species can be added compared to the latest checklist published in 2000 being
De Smedt P, Boeraeve P, Arijs G, Segers S (2018) Woodlice of Belgium: an annotated checklist and bibliography (Isopoda, Oniscidea). In: Hornung E, Taiti S, Szlavecz K (Eds) Isopods in a Changing World. ZooKeys 801: 265–304.
Woodlice (
A complete overview of the history of woodlice research in Belgium is provided, by checking all existing literature on Belgian woodlice and re-identifying all doubtful or difficult to recognise species present in the collections from the Royal Belgian Institute of Natural Sciences (RBINS). These data are complemented with extensive field surveys carried out from March 2014 until December 2017 in order to produce a new checklist of Belgian woodlice. Additionally the data of the field surveys is used to determine a status of occurrence in Belgium for all species.
The oldest record of woodlice species in Belgium dates back to 1831 (
During the second half of the 19th century, there was a slow increase in the number of publications and recorded species with nine species in 1870 and the first checklist for Belgium (
From the 1910’s to the 1970’s, most woodlouse research in Belgium focused on caves (see e.g. all publications by Leruth in the 1930’s and Kersmaekers in the 1970’s).
At the start of the 21st century, there was a renewed interest in woodlouse research with the discovery of four new species for Belgium by K. Lock (Fig.
Cumulative number of species published as part of the native fauna of Belgium between 1831 (five species) and 2017 (36 species). Exotic species exclusively living in greenhouses were omitted.
Belgium is a rather small country (ca. 30.500 km²) in Western Europe, but despite its small size, the country shows a rich geology (
All existing literature published or accepted about Belgian woodlice was reviewed if containing distribution data, descriptions, and ecology up to the end of 2017. Our search was based on old bibliographies from Belgium (
Cumulative number of publications on Belgian woodlice from 1831 until 2017.
All individuals of 18 species present in the collections of the RBINS were re-identified.
Field surveys were carried out over a four-year period from March 2014 until December 2017 by the authors together with other volunteers from “
Secondly, systematic searches of squares of the UTM 10 × 10km grid were carried out in order to map species distribution patterns across Belgium. Main woodlice biotopes were visited in every square. The biotopes visited were (1) an (ancient) forest, (2) a wetland/rivers edge or swamp forest and (3) synantropic habitat (e.g., public park, garden, graveyard…) if present in the 10 km square. These three biotopes cover the habitat niches of most woodlouse species. Additionally, 10 km squares containing a shoreline were surveyed for coastal habitats (e.g., dunes) as well. In some regions, old farms or old quarries have also been visited when present. Woodlice were hand collected by turning stones/dead wood and by sieving the litter layer.
By the end of 2017, the field survey campaign has not been completed but enough data has already been collected to assess the current status of occurrence for all species. In order to give a first indication of the distribution pattern this status is not only determined for the complete territory but also for three different topographical regions. The three regions are roughly based on the Belgian topography with lowlands in the north, hilly landscape in the centre and uplands (up to 694 m) in the south (Fig.
Map of Belgium with the UTM 10×10 km grid. The different colours indicate the different topographical regions used to determine the species status.
Data of the field surveys were used to assess the status of all species but only observations made in sufficiently surveyed squares were withhold. The criterion for a square to be sufficiently surveyed was at least five species recorded in the square. In some parts of Belgium this is about the maximum number of species that can be found so a higher lower-limit would exclude well-searched squares in those parts of Belgium. Records from heated greenhouses and of specimens only identified to genus-level were removed from the dataset. The resulting dataset contains 5110 records from March 2014 until December 2017.
For every region, at least 59.6% of the squares have been sufficiently surveyed, with a total of 254 visited squares out of 381 (66.7%) (Table
The status was assessed based on the number of squares of the UTM 10×10 km grid in which the species was recorded compared to the number of squares that have been surveyed. Six different categories are distinguished from “not present” (0% of the squares) to “very common” (more than 31.5% of the squares) (Table
Number of squares of the UTM 10×10 km grid per region and number and percentage of squares surveyed between March 2014 and December 2017.
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# | % | ||
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127 | 89 | 70.1 |
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140 | 97 | 69.3 |
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114 | 68 | 59.6 |
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381 | 254 | 66.7 |
Number of records per region and per three-month period, corresponding with the seasons of the year.
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December – February (Winter) | 525 | 617 | 174 | 1316 |
March – May (Spring) | 472 | 395 | 164 | 1031 |
June – August (Summer) | 237 | 469 | 428 | 1034 |
September – November (Autumn) | 727 | 624 | 378 | 1729 |
|
1961 | 2005 | 1144 | 5110 |
Since 1831, seven checklists have been published about Belgian woodlice (
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During the field surveys, 5110 records of woodlice in Belgium are collected between March 2014 and December 2017. For 35 of the 36 Belgian species there is at least one record in the database (Table
Map of Belgium with the number of species per square of the UTM 10×10 km grid.
Status categories for the Belgian woodlice, together with the lower and upper limits for the percentage of squares where a species was recorded between March 2014 and December 2017 in a certain region.
Status | No. of squares | Rel. no. of squares |
---|---|---|
Not present | 0 | 0% |
Very rare | 1–5 | < 1.3% |
Rare | 6–15 | 1.3–3.9% |
Rather common | 16–40 | 3.9–10.5% |
Common | 41–120 | 10.5–31.5% |
Very common | > 120 | > 31.5% |
Number of visited squares where a certain species is recorded and their relative occurrence per region and countrywide.
Species | North | Centre | South | Belgium | ||||
---|---|---|---|---|---|---|---|---|
# | % | # | % | # | % | # | % | |
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9 | 10.1 | 44 | 45.4 | 18 | 26.5 | 71 | 28.0 |
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1 | 1.1 | 0 | 0.0 | 0 | 0.0 | 1 | 0.4 |
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27 | 30.3 | 46 | 47.4 | 31 | 45.6 | 104 | 40.9 |
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0 | 0.0 | 7 | 7.2 | 22 | 32.4 | 29 | 11.4 |
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0 | 0.0 | 11 | 11.3 | 20 | 29.4 | 31 | 12.2 |
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2 | 2.2 | 13 | 13.4 | 12 | 17.6 | 27 | 10.6 |
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62 | 69.7 | 53 | 54.6 | 16 | 23.5 | 131 | 51.6 |
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2 | 2.2 | 0 | 0.0 | 4 | 5.9 | 6 | 2.4 |
|
3 | 3.4 | 0 | 0.0 | 0 | 0.0 | 3 | 1.2 |
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44 | 49.4 | 29 | 29.9 | 7 | 10.3 | 80 | 31.5 |
|
30 | 33.7 | 15 | 15.5 | 4 | 5.9 | 49 | 19.3 |
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1 | 1.1 | 34 | 35.1 | 37 | 54.4 | 72 | 28.3 |
|
11 | 12.4 | 26 | 26.8 | 10 | 14.7 | 47 | 18.5 |
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2 | 2.2 | 0 | 0.0 | 0 | 0.0 | 2 | 0.8 |
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37 | 41.6 | 63 | 64.9 | 63 | 92.6 | 163 | 64.2 |
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9 | 10.1 | 2 | 2.1 | 0 | 0.0 | 11 | 4.3 |
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0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
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89 | 100.0 | 92 | 94.8 | 68 | 100.0 | 249 | 98.0 |
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3 | 3.4 | 34 | 35.1 | 10 | 14.7 | 47 | 18.5 |
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87 | 97.8 | 90 | 92.8 | 62 | 91.2 | 239 | 94.1 |
|
38 | 42.7 | 26 | 26.8 | 18 | 26.5 | 82 | 32.3 |
|
2 | 2.2 | 4 | 4.1 | 0 | 0.0 | 6 | 2.4 |
|
0 | 0.0 | 1 | 1.0 | 0 | 0.0 | 1 | 0.4 |
|
0 | 0.0 | 0 | 0.0 | 3 | 4.4 | 3 | 1.2 |
|
88 | 98.9 | 93 | 95.9 | 65 | 95.6 | 246 | 96.9 |
|
65 | 73.0 | 77 | 79.4 | 62 | 91.2 | 204 | 80.3 |
|
13 | 14.6 | 7 | 7.2 | 2 | 2.9 | 22 | 8.7 |
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0 | 0.0 | 4 | 4.1 | 29 | 42.6 | 33 | 13.0 |
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37 | 41.6 | 29 | 29.9 | 8 | 11.8 | 74 | 29.1 |
|
40 | 44.9 | 20 | 20.6 | 0 | 0.0 | 60 | 23.6 |
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0 | 0.0 | 10 | 10.3 | 7 | 10.3 | 17 | 6.7 |
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32 | 36.0 | 15 | 15.5 | 0 | 0.0 | 47 | 18.5 |
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0 | 0.0 | 1 | 1.0 | 2 | 2.9 | 3 | 1.2 |
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55 | 61.8 | 36 | 37.1 | 7 | 10.3 | 98 | 38.6 |
|
69 | 77.5 | 64 | 66.0 | 55 | 80.9 | 188 | 74.0 |
|
23 | 25.8 | 39 | 40.2 | 14 | 20.6 | 76 | 29.9 |
Although many papers have been published on woodlice, many records remained doubtful and the reference collection at the RBINS contained a considerable number of identification errors. Additionally, the number of species recorded in Belgium was relatively low compared to neighbouring countries. This new checklist adds nine species to the last checklist published only 17 years ago (
Certain exotic species are in Belgium only recorded from greenhouses and do not have free-living populations. These species are discussed in a recent paper dedicated to greenhouse species in Belgium (
Expected to occur in Belgium by
First mentioned from greenhouses by
First mentioned by
First reported record of the species was done by
Discovered in Belgium through pitfall trap research in 1998 (
Reported by
Only two sightings of this species are known in Belgium. After its discovery in 1999 (
Expected to occur in Belgium by
First individuals identified by
First recorded by
Discovered in 2015 (
First recorded by
First mentioned by
The bibliography presented below should be considered as a bibliography for the species complex
One of the first five species mentioned for the fauna of Belgium by
Expected to occur in Belgium by
One of the five first species mentioned for the fauna of Belgium by
First recorded by Mac Leod (1880), and appeared to be common but undersampled (
Discovered by
Expected to occur in Belgium by
First mentioned by
Mentioned for the first time for Belgium by
One of the five first species on the Belgian list (
Discovered for the first time in Belgium in 2016 (
Expected to occur in Belgium by
First mentioned by
One of the first five species mentioned for the country by
Expected to occur in Belgium by
One of the first five species mentioned for the fauna of Belgium by
First mentioned by
First observations from the 1870’s and first mentioned by
First recorded by
First mentioned by
Six of the nine species added to this new checklist,
Six species were mentioned on at least one of the previous checklists, but are not present anymore on the current checklist. Most species appeared to be misidentifications or could not be confirmed because material was not preserved and literature citings are incomplete.
Literature on Belgian woodlice in greenhouses is very limited. Only five papers deal with inventories carried out in Belgian greenhouses and they are all from the northern part of the country. Up to date only four exotic species could be confirmed in Belgian greenhouses. They cannot be considered as part of the Belgian woodlice fauna, because of the lack of wild populations, and are not included in this checklist as Belgian species. However, they were included in previous checklists (see e.g.
The first exotic species recorded from Belgian greenhouses is
Twenty-five percent of the Belgian woodlice species were added on this new checklist and all were discovered the last 20 years, therefore it is still possible that even more species can be discovered in Belgium. Below, some species recorded in neighbouring countries and relatively close to the Belgian border are listed:
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Three of the last five new species on the Belgian list are large to medium-sized and therefore it is possible that the above-mentioned species are present and awaiting discovery.
With 36 species Belgium now has a comparable amount of species, relative to its size, to neighbouring countries like the Netherlands (33 species see
We are grateful to Yves Samyn and Wouter Dekoninck for giving us access to the collections of the RBINS. Oliver Mechthold is thanked for the help with fieldwork.
The list below represents the bibliography of Belgian woodlice with other references used in the text: these other references not dealing directly with Belgian woodlice are indicated with an asterisk [*].