Ligidium hypnorum Cuvier, 1792

Figs 4B, 5A

Published sources.Herold 1930: 478–479; Vilbaste and Vilbaste 1993: 317.

Studied material. 117 specimens from 13 localities (loc. 30a, 47b, 47c, 54c, 57b, 83c, 87a, 87b, 88a, 89a, 92a, 95a, 95b).

Comments. A locally abundant species, with no records from Estonian islands. It has been described as widespread in Estonia also in the past (Herold 1930). The findings are from different habitats: fresh to mesic forests, meadows, arable fields and gardens. Present also in Lithuania (Vilisics et al. 2012) and Latvia (Spuņģis 2008) but not Finland (Boxshall G 2013).

Trichoniscus pusillus Brandt, 1833

Figs 3A, 5B

Published sources.Herold 1927: 6; Herold 1928: 215; Herold 1930: 479 (as T. elisabethae Herold, 1923; T. elisabethae var. estoniensis Herold, 1927; T. caelebs Verhoeff, 1917); Vilbste 1970: 170 (as T. pusillus caelebs Vh.); Vilbaste et al. 1985: 151 (as T. pusillus caelebs Vh.); Remm 1988: 127 (as T. pusillus caelebs Vh.); Vilbaste and Vilbaste 1993: 317.

Studied material. 117 specimens from 24 localities (loc. 1e, 4d, 17a, 23b, 25a, 34a, 35a, 39a, 40c, 47a, 50a, 51a, 57a, 58c, 68a, 74a, 78a, 78b, 78e, 80a, 80d, 83a, 89b, 92a).

Comments. Once reported as the most common species of Trichoniscidae (e.g. Herold 1927, 1930), the species appears to have become less abundant. It is widespread in various habitats (bogs, different types of forests, meadows, and urban areas), but is more common in moist habitats and is often associated with decaying wood. The species is known to be mainly parthenogenetic (Gruner 1966; De Smedt et al 2016), and the collected material consisted only of female specimens. Thus, no male characters were available for study and it cannot be ruled out that some specimens were misidentified and other Trichoniscus species may also be present in Estonia as very rare (e.g. T. provisorius or T. pygmaeus). The taxonomic status of the described varieties T. elisabethae Herold, 1923 and T. elisabethae var. estoniensis Herold, 1927 is unclear, but we follow the Schmalfuss (2003) catalogue and treat them as T. pusillus. Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946; Vilisics and Terhivuo 2009).

* Hyloniscus riparius (C. Koch, 1838)

Figs 3B, 5C

Studied material. 202 specimens from 22 localities (loc. 12a, 23b, 35b, 39a, 39a, 49a, 50a, 52b, 53a, 55b, 57a, 58b, 59a, 60b, 61a, 69c, 70b, 78a, 78e, 78g, 83a, 85a).

Comments. The species is widespread and common, but has only recent records and is probably extending its range in the Europe. It has been often found in human settlements, but also seashore habitats and different types of forests, except the very dry ones. Present also in Latvia (Spuņģis 2008) and Finland (Vilisics and Terhivuo 2009).

Haplophthalmus mengii (Zaddach, 1844)

Fig. 5D

Published source.Herold 1930: 479–480.

Comments. Reported as rare, with only one finding locality in northern Estonia (Herold 1930). No recent records. Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

* Platyarthrus hoffmannseggii Brandt, 1833

Figs 4A, 5E

Studied material. 3 specimens from 1 locality (loc. 80g).

Comments. A myrmecophilous species, found from a nest of Lasius niger (Linnaeus, 1758). There are no records from the northern Baltic region so far, but it has recently been found in Lithuania (Šatkauskienė 2017), and a population has also been found in Finland (Lehtinen 1961). However, due to the destruction of the only known locality, the species could be extinct there now (Vilisics and Terhivuo 2009).

Trachelipus rathkii (Brandt, 1833)

Figs 2A, 5F

Published sources.Herold 1927: 52 (as Porcellio rathkei); Herold 1930: 476 (as Tracheoniscus rathkei (Brandt, 1833)); Vilbaste 1970: 170 (as Tracheoniscus rathkei (Brandt, 1833)); Vilbaste et al. 1985: 151 (as Tracheoniscus rathkei (Br.)).

Studied material. 3180 specimens from 114 localities (loc. 1a, 1c, 1e, 1f, 3a, 3b, 4c, 6a, 7a, 9a, 9b, 10a, 10b, 11a, 12a, 13a, 14b, 15a, 15b, 16a, 17a, 17b, 17c, 17d, 18a, 18b, 18c, 19a, 20a, 21a, 22a, 23a, 23b, 23c, 25a, 27a, 28a, 28b, 29a, 30a, 30c, 30d, 33a, 33b, 34a, 34b, 35b, 35b, 35c, 35c, 37a, 38a, 39a, 40a, 40b, 41a, 41b, 42a, 46b, 51a, 51b, 52a, 52b, 53a, 55a, 56a, 57a, 58a, 58b, 59a, 60b, 61a, 62a, 63b, 64a, 65a, 66a, 66b, 66c, 66c, 67a, 68b, 69a, 69b, 70a, 71a, 72a, 73a, 76a, 77a, 78a, 78d, 78e, 78f, 78f, 79a, 80a, 80b, 80c, 80d, 81a, 81b, 81c, 82a, 83a, 84a, 85a, 86a, 87a, 90a, 91a, 91b).

Comments. One of the most common species in Estonia, in all kinds of habitats (both anthropogenic and natural, except bogs). It has also been described as widespread and common in Estonia in the past (Herold 1927, 1930). Present also in Leningrad region (European Russia, Kuznetsova and Gongalsky 2012), Latvia (Spuņģis 2008), and Finland (Palmén 1946).

Porcellio scaber Latreille, 1804

Figs 2B, 5G

Published sources.Herold 1927: 52; Herold 1930: 481; Vilbaste et al. 1985: 151.

Studied material. 217 specimens from 13 localities (loc. 3b, 24a, 26a, 26b, 30b, 35c, 46b, 48a, 63a, 78c, 78e, 78f, 84a).

Comments. The species was described as purely synanthropic in continental Estonia and free-living in western Estonian islands (Herold 1927, 1930). The studied material contains findings from and outside of human settlements (including different forests, grasslands, and seashore) both from western islands and continent. Present also in Novgorod region (European Russia, Kuznetsova and Gongalsky 2012), Latvia (Spuņģis 2008), and Finland (Palmén 1946).

Porcellio spinicornis Say, 1818

Figs 2C, 5H

Published sources.Herold 1927: 52; Herold 1930: 481 (as P. pictus Brandt, 1833); Vilbaste et al. 1985: 151 (as P. pictus Br.).)

Studied material. 68 specimens from 19 localities (loc. 4b, 6b, 20b, 32a, 35b, 39a, 40b, 46a, 51c, 52b, 60a, 61a, 78f, 78h, 78i, 84a, 89a, 93a, 97).

Comments. A common and widespread species, often found on stone walls in human settlements, but also in mesic deciduous forests. Present also in Leningrad region (European Russia, Kuznetsova and Gongalsky 2012), Latvia (Spuņģis 2008), and Finland (Palmén 1946).

Porcellionides pruinosus (Brandt, 1833)

Published source.Herold 1930: 476.

Comments. No recent records. This species has been described as purely synanthropic in Estonia (Herold 1930). Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Cylisticus convexus (De Geer, 1778)

Figs 2D, 5I

Published sources.Herold 1927: 51; 480 Herold 1930: 480.

Studied material. 825 specimens from 5 localities (loc. 46b, 66a, 78e, 78f, 78g).

Comments. This species is widespread and locally quite abundant, both in human settlements and in forests, under stones or in rotten logs. It has been described as widespread and mainly synanthropic in Estonia by W. Herold, with free-living populations in northern and western Estonian islands (Herold 1930). Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Oniscus asellus Linnaeus, 1758

Figs 2E, 5J

Published sources.Fischer 1778: 167 (questionable; see comment in Introduction); Herold 1930: 480.

Studied material. 433 specimens from 5 localities (loc. 4b, 6, 36b, 47b, 48b).

Comments. The species seems to be free-living on the island of Saaremaa, but synanthropic and sometimes quite abundant elsewhere. Herold (1930) described it as being widespread but purely synanthropic in Estonia. Present also in Latvia (Spuņģis 2008), Pskov region (European Russia, Kuznetsova and Gongalsky 2012), and Finland (Palmén 1946).

Armadillidium opacum (Koch, 1841)

Figs 3D, 5K

Published sources.Herold 1927: 53; Herold 1930: 483–485; Vilbaste et al. 1985: 151.

Studied material. 5294 specimens from 44 localities (loc. 1a, 1b, 1c, 1d, 1e, 1f, 2a, 2b, 2c, 4b, 5a, 6a, 8a, 8c, 9a, 9b, 11a, 13a, 14a, 14b, 14c, 14c, 15b, 16a, 17a, 17b, 17c, 17d, 18b, 19a, 20a, 21a, 23a, 23c, 25a, 25b, 27a, 28a, 28b, 29a, 30a, 30d, 31a, 35a, 37a).

Comments. Very common in western Estonia and islands (in forests, grasslands, and coastal habitats) but rare elsewhere. Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Armadillidium pictum Brandt, 1833

Fig. 5L

Published sources.Herold 1927: 53; Herold 1930: 482–483.

Studied material. 5 specimens from 3 localities (loc. 28a, 44a, 45a).

Comments. A rare species found only in northern Estonia and Muhu island in coastal habitats (broad-leaved forest under limestone escarpment, pine forest near seashore, alvar grassland). Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Armadillidium pulchellum (Zenker, 1798)

Figs 3E, 5M

Published sources.Herold 1930: 481–482; Vilbaste et al. 1985: 151.

Studied material. 1 specimen from 1 locality (loc. 4d).

Comments. A rare species found only on Saaremaa island in western Estonia (in a spring fen). Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Armadillidium vulgare (Linnaeus, 1758)

Fig. 5O

Published source.Chinery 2005: 300.

Studied material. 1 specimen from 1 locality (loc. 81a).

Comments. A rare synanthropic species with only one finding from Estonia (from suburban area in Tartu). Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).

Armadillidium zenckeri Brandt, 1833

Figs 3C, 5N

Published sources.Herold 1927: 53; Herold 1930: 485–490; Vilbaste 1970: 170; Vilbaste et al. 1985: 151.

Studied material. 452 specimens from 44 localities (loc. 1a, 1b, 1d, 1e, 1f, 2a, 2b, 2c, 3a, 4a, 4c, 4e, 5a, 7a, 8b, 9a, 9b, 11a, 13a, 14a, 14b, 15b, 16a, 17a, 17b, 17c, 17d, 19a, 20a, 21a, 23a, 23b, 23c, 25a, 28a, 28b, 29a, 30a, 30d, 36a, 37a, 37a, 37a, 43a).

Comments. Common in western Estonia and islands, but rare elsewhere. Present in dry to mesic forests and different grasslands. Present also in Latvia (Spuņģis 2008) and Finland (Palmén 1946).