Parachernes sp.

Mahnert, Volker, 2014, Pseudoscorpions (Arachnida: Pseudoscorpiones) from the Galapagos Islands (Ecuador), Revue suisse de Zoologie 121 (2), pp. 135-210 : 197-205

Parachernes sp.

SPECIMENSSTUDIED: Floreana: RBINS; 1P; BlackBeach, Cryptocarpus litter, 24.III. 1989, leg. S. Peck (89-149) . – Isabela: RBINS; 1T; 4 km NW Santo Tomas , 500 m, moss in forest, litter, 14.III.1989, leg. S. Peck (89-129) . – Pinta : RBINS; 1T; alt. 540 m, 20-22.III.1986, leg. L. Baert, J.-P. Maelfait & K. Desender (B.86/141).

REMARK: The immature specimens could not identified to species level. Considering the length of the tarsal pseudotactile seta, they either belong to P. galapagensis or to P. franzi .

WITHIIDAE

Withius piger ( Simon, 1878) Figs 74-75

Cheliferpiger Simon, 1878: 148-149 ( Algeria).

SPECIMENS STUDIED: Santa Cruz: 39342; 1T; CDRS, buildings, 1978, leg. W. G. Reeder (?) . – 83 3♀ 4T 2D; CDRS, 10 m, tortoisedungandhay, 7.II.1989, leg. S. Peck (89-36) . – 1♀; Puntudo , 700 m, pampazone, horsedung, 8.II.1989, leg. S. Peck (89-42).

SHORT DESCRIPTION (based on 43 1♀): Sternites: stigmata of sternite III with 2-3 setae, those of IV with 2-4 (frequently 3) setae; glandular setae arranged in triangular patches on male half-tergites: IV 5-10, V 20-32, VI 28-37, VII 31-35, VIIII 24-42, IX 13-25, X 0-2; ♀: half-sternitesV-Xwith 1-2 glandularsetaeeach. Chelicera: hand with 5 setae, the two basal ones apically dentate; galea of 3 short, with 3 or 4 tiny apical teeth, that of ♀ long, with 6 apical/subapical branchlets; serrula exterior with 16-18 lamellae, rallum with 4 setae, the anteriormost dentate. Pedipalps (3) (Figs 74-75): femur 3.1-3.5 (♀ 2.9) times, patella 2.8-3.2 (♀ 2.5) times, handwithpedicel 2.2-2.6 (♀ 2.1) times, chelawithpedicel 3.6-3.9 (♀ 3.2) timeslongerthanbroad, hand with pedicel 1.4-1.6 (♀ 1.5) times longer than finger; chelal finger slightly gaping FIGS 74-75

Withius piger ( Simon, 1878) , 3. (74) Left pedipalp. (75) Trichobothrial pattern. Scale units 0.1 mm.

(indistinctly in ♀); fixed finger with 28-31 (♀ 25) broad cusped teeth, movable finger with 31-35 (♀ 29) marginal teeth and one distal lateral one; trichobothrium ist in dorsal, it inparaxialposition, est levelwith it. LegIV (3♀): femur+patella 2.8-3.0 times, tibia 3.7-4.2 times, tarsus 4.5-5.0 timeslongerthandeep, tibia 1.29-1.37 times longerthantarsus, tarsuswithlongtactilesetainmiddle ( TS =0.54-0.60); undivided arolia nearly as long as smooth claws .

MEASUREMENTS inmmof 3 (♀): Pedipalps: femur 0.60-0.77/0.19-0.23 (0.58/0.20), patella 0.63-0.80/0.22-0.25 (0.59/0.23), handwithpedicel 0.61-0.78/0.27- 0.30 (0.63/0.30), lengthofpedicel 0.08-0.09 (0.07), ofmovablefinger 0.42-0.49 (0.42), ofchelawithpedicel 0.97-1.17 (0.97). LegIV (3♀): femur+patella 0.51- 0.62/0.18-0.22, tibia 0.42-0.48/0.10-0.11, tarsus 0.30-0.35/0.06-0.07.

REMARKS: The specimens correspond in most details to the descriptions given by Vachon (1970) and Heurtault (1971a, b). Males from Santa Cruz show a more slender pedipalpal patella, being as slender as that of Withius rebieri Heurtault, 1971 . Vachon (1970) indicated for the type specimen of W. piger a patella 2.65 times longer than broad. The introduction of this species to Santa Cruz has probably taken place quite recently, since its presence is limited to the Charles Darwin Research Station, the tritonymph found on horse dung might have been transported by a horse.

I also attribute to Withius piger several specimens (5 3), collected from Bermuda ( Somerset Island , leg. R. Schuster, in forest near “alter Bahnstrasse ”, 6.IX.1981) , forwhichthepedipalpalpatellais 2.69-3.06 timeslongerthanbroad. The species is of cosmopolitan distribution, and it is here recorded for the first time from the Galapagos archipelago and from Bermuda.

Identification key to adults of the pseudoscorpion species recorded from Galapagos

1a Chelal fingers without venom apparatus; trichobothrium xs present on fixed chelal finger, legs I/II with one, III/IV with two tarsal articles (Chthonioidea)................................................ 2

1b One or both chelal fingers with venom apparatus; trichobothrium xs absent on fixed chelal finger; all legs with equal number of tarsal articles... 8

2a Dorsum of chelal hand with two trichobothria (Chthoniidae)............. 3

2b Dorsum of chelal hand with 4 trichobothria (Lechytiidae)...................................................... Lechytia chthoniiformis

3a Coxal spines present on coxae II only.............................. 4

3b Coxal spines present on coxae I and II....... Pseudochthonius galapagensis

4a Pedipalpal hand with at least two long spine-like setae on distal paraxial face; eyes distinct.............................................. 5

4b Pedipalpal hand with only one long and thin seta on distal paraxial face; eyes indistinct.............................. Tyrannochthonius albidus

5a Large species, length of pedipalpal chela at least 1.0 mm; teeth on movable chelal finger flattened, retrorse and densely set................ 6

5b Small species, length of pedipalpal chela at most 0.90 mm (3♀); teeth of movable finger straight and distinctly spaced; pedipalpal femur 4.6 times (♀)-5.1 times (3) longer than broad... Paraliochthonius litoralis sp. n.

6a Pedipalpal femur 4.7-5.2 times, patella 2.1-2.3 times longer than broad..... 7

6b Pedipalpal femur 5.6-6.1 times, patella 2.5-2.6 times longer than broad; length of chela 1.47 mm (3♀)........ Paraliochthonius galapagensis sp. n.

7a Pedipalpal femur 0.69-0.80 mm long, hand 1.75-1.81 times (length 0.35- 0.42 mm) longer than deep, chela 5.0-5.2 times longer than deep, length 3 1.02-1.12 mm, ♀ 1.08-1.20 mm ......... Paraliochthonius rupicola sp. n.

7b Pedipalpal femur 0.84-0.96 mm, hand 1.9-2.0 times (length 0.45- 0.51 mm), chela 5.4-5.7 times longer than deep, length 3 1.26-1.34 mm, ♀ 1.32-1.45 mm ......................... Paraliochthonius pecki sp. n.

8a Movable cheliceral finger with several teeth; seta gs submedial; trichobothrium t on movable chelal finger lanceolate ( Syarinidae )............. 9

8b Movable cheliceral finger with 1-2 subapical teeth; seta gs subdistal; trichobothrium t on movable chelal finger fine, simple................. 10

9a Large species with slender pedipalps, femur 2.9-3.0 times longer than broad (length 0.58-0.59 mm), chela with pedicel 2.9 times longer than broad (length 0.94-0.97 mm)............. Ideoblothrus galapagensis sp. n.

9b Small species with stout pedipalps, femur 2.5-2.6 times longer than broad (length 0.32-0.39 mm), chela with pedicel 2.3-2.6 times longer than broad (length 0.54-0.66 mm)............ Ideoblothrus emigrans sp. n.

10a Carapace subtriangular, posteriorly distinctly broader than anteriorly; long cucullus present, eyes situated away from anterior margin of carapace.................................................... 11

10b Carapace parallel-sided; long cucullus absent, eyes situated near anterior margin of carapace............................................ 13

11a Four eyes present; large species, femur length at least 1.13 mm (Garypidae)................................ Garypus granosus sp. n.

11b Two eyes; small species, femur length about 0.30 mm (Cheiridiidae)...... 12

12a Movable chelal finger with one trichobothrium; posterior margin of carapace and anterior tergites without protruding granula................................................. Neocheiridium galapagoense

12b Movable chelal finger with 2 trichobothria; posterior margin of carapace and anterior tergites with protruding granula...................................................... Cryptocheiridium confundens sp. n.

13a Spermatheca absent; pedipalpal femur with 1-2 tactile setae; legs with two tarsal segments........................................... 14

13b Spermatheca present; pedipalpal femur without trichobothria; legs with only one tarsal segment......................................... 21

14a Tergites undivided; tarsal arolia undivided (Olpiidae).................. 15

14b Tergites divided; tarsal arolia divided (Garypinidae)................... 17

15a Trichobothrium est halfway between ist / it and isb; chelal hand cordi- form, fixed chelal finger distinctly longer than hand with pedicel; setae on tergite XI forked........................................... 16

15b Trichobothrium est distinctly nearer to it / ist than to isb; chelal hand not cordiform; fixed chelal finger as long as hand with pedicel; setae on tergite XI simple.............................. Stenolpium insulanum

16a Large species; length of pedipalpal femur 0.61-0.81 mm, of patella 0.51- 0.69 mm, of chela with pedicel 1.03-1.46 mm ... Aphelolpium longidigitatum

16b Smaller species; length of pedipalpal femur 0.45-0.54 mm, of patella 0.35-0.45 mm, of chela with pedicel 0.71-0.93 mm .... Aphelolpium cayanum

17a Pedipalpal chela with normal number of trichobothria (8 on fixed, 4 on movable finger)............................................... 18

17b Pedipalpal chela with reduced number of trichobothria (7 on fixed finger, 2 on movable finger)...................... Galapagodinus franzi

18a Arolia distinctly longer than claws, divided for half of total length; cheliceral hand with 5 setae..................................... 19

18b Arolia barely longer than claws, divided for one third of total length; cheliceral hand with 4 setae................... Serianus maritimus sp. n.

19a Pedipalps stout, femur 2.8-3.4 times, chela with pedicel 2.9-3.6 times longer than broad............................................. 20

19b Pedipalps slender, femur 4.8 times, chela with pedicel 5.2 times longer than broad................................. Serianus elongatus sp. n.

20a Tergites I/II with 4-6, tergites III-V with 5-6, tergites VI-X with 7-8 marginal setae.................................... Serianus cf. galapagoensis

20b Tergites I-V with 4, VI-X with 6 marginal setae..... Serianus galapagoensis

21a Male sternites with patches of glandular setae; female sternites V-VIII with a median pair of glandular setae; junction between femur/patella of legs I and II perpendicular ( Withiidae )..................... Withius piger

21b Male sternites without patches of glandular setae; female sternites V-VIII without a pair of glandular setae; junction between femur/patella of legs I and II oblique......................................... 22

22a Venom apparatus present in movable finger; tarsi proximally with raised slit sensillum; chelal fingers normally with at least one accessory tooth ( Chernetidae )................................................ 23

22b Venom apparatus only present in fixed chelal finger; tarsi proximally without raised slit sensillum; chelal fingers without accessory teeth (Atemnidae)............................... Paratemnoides nidificator

23a Trichobothrium est of fixed chelal finger on level with ist / it .................................................. Rhopalochernes insulanus

23b Trichobothrium est distinctly proximal to ist / it ....................... 24

24a Pseudotactile seta of tarsus of leg IV finely dentate near apex, shorter than, or as long as, depth of tarsus; tergite XI with two clavate lateral setae; pedipalps slender (femur at least 2.5 times longer than broad), pedipalpal femur obliquely enlarged basolaterally; spermatheca consisting of two tubes with ovoid apical enlargements..................... 25

24b Tactile seta of leg IV smooth, distinctly longer than depth of tarsus; tergite XI with two fine dentate lateral setae; pedipalps stout, femur 2.1- 2.4 (rarely 2.5 or 2.6)(3)/2.2-2.5 (♀) times longer than broad, pedipalpal femur abruptly enlarged basolaterally; spermatheca consisting of two tubes without apical enlargements............... Parachernes nigrimanus

25a Pedipalps slightly more slender, femur 2.5-3.1 (mostly 2.8-3.1)(3)/2.6- 3.3 (mostly 2.9-3.3) (♀) times, patella 2.4-2.6 (3)/2.3-2.7 (♀) times, chela with pedicel 3.0-3.4 (3)/2.8-3.3 (♀) times longer than broad; whitish lateral spots on posterior margin of carapace tapering laterally............................................... Parachernes franzi

25b Pedipalps slightly less slender, femur 2.4-2.9 (3)/ 2.4-2.8 (♀) times, patella 2.0-2.5 (3)/(2.2-2.5 (♀) times, chela with pedicel 2.4-3.2 (mostly 2.4-2.9) (3)/2.4-3.1 (mostly 2.4-2.9)(♀) times longer than broad; lateral whitish spots on posterior margin of carapace not tapering laterally.................................. Parachernes galapagensis

LIST OF ISLANDS AND THEIR RECORDED PSEUDOSCORPION SPECIES (island data mainly from Peck, 1990, and from www.wikipedia.org/wiki/ Galapagos; with surface area and maximal elevation in parentheses.

Baltra (= South Seymour) (25 km 2 - 50 m)

Aphelolpium longidigitatum; Serianus cf. galapagoensis

Bartolomé (1.2 km 2 - 114 m)

Lechytia chthoniiformis, Neocheiridium galapagoense, Parachernes galapagensis

Champion (NE Floreana) (9,4 ha -? m)

Serianus galapagoensis , Cryptocheiridium confundens sp. n.

Darwin (1.1 km 2 - 168 m)

Paraliochthonius rupicola sp. n.

Espanola (58 km 2 - 198 m)

Aphelolpium cayanum, Aphelolpium longidigitatum, Serianus galapagoensis , Cryptocheiridium confundens sp. n., Parachernes galapagensis , Parachernes nigrimanus

Fernandina (635 km 2 - 1494 m)

Paraliochthonius galapagensis sp. n., Paraliochthonius rupicola sp.n., Serianus galapagoensis , Serianus maritimus sp. n., Galapagodinus franzi , Garypus granosus sp. n., Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Parachernes franzi , Parachernes galapagensis , Parachernes nigrimanus

Floreana (= Santa Maria) (171 km 2 - 640 m)

Pseudochthonius galapagensis, Lechytia chthoniiformis, Ideoblothrus emigrans sp. n., Aphelolpium cayanum, Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis, Neocheiridium galapagoense, Parachernes galapagensis , Parachernes nigrimanus

Gardner (at Espanola) (0.58 km 2 - 49 m) (data from Schatz, 1998)

Aphelolpium cayanum, Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis

Gardner (at Floreana)

Pseudochthonius galapagensis , Ideoblothrus galapagensis sp. n., Aphelolpium sp. (A. longidigitatum?), Neocheiridium galapagoense

Genovesa (= Tower) (17 km 2 - 76 m)

Lechytia chthoniiformis, Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis, Neocheiridium galapagoense, Parachernes franzi , Parachernes sp. ( P. galapagensis ?)

Isabela (=Albemarle) (4670 km 2 - 1707 m)

Paraliochthonius litoralis sp. n., Paraliochthonius pecki sp. n., P seudochthonius galapagensis, Lechytia chthoniiformis, Aphelolpium cayanum, Aphelolpium longidigitatum, Stenolpium insulanum, Galapagodinus franzi , Serianus elongatus sp. n., S erianus galapagoensis , Garypus granosus sp. n., Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Paratemnoides nidificator , Parachernes franzi , Parachernes galapagensis , Parachernes nigrimanus, Rhopalochernes insulanus

Marchena (173 km 2 - 343 m)

Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis , Parachernes franzi , Parachernes galapagensis , Parachernes nigrimanus

North Plazas

Aphelolpium longidigitatum, Parachernes galapagensis

Pinta (60 km 2 - 780 m)

Galapagodinus franzi , Serianus galapagoensis , Serianus maritimus sp. n., Garypus granosus sp. n., Neocheiridium galapagoense, Parachernes franzi , Parachernes galapagensis

Pinzon (= Duncan) (18 km 2 - 458 m)

Pseudochthonius galapagensis, Lechytia chthoniiformis, Ideoblothrus emigrans sp. n., Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis , Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Parachernes galapagensis

Rabida (4.9 km 2 - 367 m)

Ideoblothrus emigrans sp. n., Garypus granosus sp. n., Parachernes galapagensis , Parachernes nigrimanus

San Cristobal (552 km 2 - 715 m)

Aphelolpium cayanum, Aphelolpium longidigitatum, Stenolpium insulanum, Galapagodinus franzi , Serianus galapagoensis , Serianus maritimus sp. n., Garypus granosus sp. n., Parachernes nigrimanus

Santa Cruz (=Indefatigable) (904 km 2 - 864 m)

Paraliochthonius litoralis sp. n., Pseudochthonius galapagensis , Tyrannochthonius albidus, Lechytia chthoniiformis, Ideoblothrus emigrans sp. n., Aphelolpium longidigitatum, Stenolpium insulanum, Galapagodinus franzi , Serianus galapagoensis , Serianus maritimus sp. n., Garypus granosus sp. n., Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Paratemnoides nidificator , Parachernes galapagensis , Parachernes nigrimanus, Withius piger

Santa Fé (=Barrington) (24 km 2 - 259 m)

Paraliochthonius rupicola sp. n., Pseudochthonius galapagensis, Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis , Serianus maritimus sp. n., Garypus granosus sp. n., Neocheiridium galapagoense, Parachernes galapagensis , Parachernes nigrimanus

Santiago (572 km 2 - 905 m)

Pseudochthonius galapagensis, Lechytia chthoniiformis, Aphelolpium longidigitatum, Galapagodinus franzi , Serianus galapagoensis , Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Parachernes galapagensis , Parachernes nigrimanus

Seymour (1.9 km 2 - 28 m)

Galapagodinus franzi , Serianus galapagoensis, Neocheiridium galapagoense, Parachernes galapagensis , Parachernes nigrimanus

Sombrero Chino (0.25 km 2 - 98 m)

Serianus cf. galapagoensis , Cryptocheiridium confundens sp. n.

South Plazas (0.13 km 2 - 23 m)

Lechytia chthoniiformis, Aphelolpium longidigitatum, Serianus galapagoensis , Cryptocheiridium confundens sp. n., Neocheiridium galapagoense, Parachernes franzi , Parachernes galapagensis

Venecia (close to Santa Cruz)

Aphelolpium longidigitatum

Wolf (1.3 km 2 - 253 m)

Serianus maritimus sp. n.

CONCLUSIONS

Ten families and 25 species are identified in the examined collections consisting of 509 samples (= 509 localities with higly diversified habitats and various sampling methods) and assembled since 1965, the pseudoscorpion fauna of this archipelago is now quite well known. It is evident from the number of samples that the easily accessible islands, with human settlements and good roads or paths, have been more intensively sampled than the smaller islands, e.g. Baltra, Darwin, Venecia and Wolf wherefrom only one or two species are known from one locality. It is also evident that a survey on the bigger islands with a higher elevation and a higher diversification of habitats yielded a higher number of species, without implying that the size of an island represents the most important factor for the number of species.

The families Chthoniidae (3 genera, 6 species), Garypinidae (2 genera, 4 named species) and Chernetidae (2 genera, 4 species) are the most diversified ones. The most frequent and abundant species are Parachernes galapagensis (16 islands, 59 localities, 367 specimens), Aphelolpium longidigitatum (15 islands, 66 localities, 109 specimens), Neocheiridium galapagoense (15 islands, 39 localities, 115 specimens), Galapagodinus franzi (14 islands, 83 localities, 239 specimens), Parachernes nigrimanus (11 islands, 59 localities, 76 specimens), Cryptocheiridium confundens sp. n. (9 islands, 14 localities, 78 specimens), Garypus granosus sp. n. (7 islands, 14 localities, 115 specimens) and Pseudochthonius galapagensis (6 islands and 19 localities, but only 37 specimens). All but one (A. longidigitatum) are considered as species endemic to the archipelago. One genus is endemic to the archipelago (Galapagodinus). The number of endemic species represents four-fifth (20) of the 25 species recorded. Most of the endemic species are widely distributed and found on several islands and isles, which might indicate an early diversification and a long-lasting dispersal activity. Only few species are recorded from one or two islands and from one to three localities only, but this rarity probably has no ecological/biological background, but probably from insufficiently explored habitats. The four Paraliochthonius species, but also Garypus granosus , have been collected mainly by one collector (S. Peck) using a particular collecting method (cliff spraying). Serianus elongatus and Tyrannochthonius albidus , known from one locality each, with one respectively two specimens, are likely colonizing the mesovoid shallow substratum ( MSS) or lava tubes. These habitats are unexplored on the Galapagos islands.

Only five species out of the 25 recorded ones have their original distribution area outside the archipelago and are evidently introduced. Lechytia chthoniiformis and Paratemnoides nidificator are widely distributed on continental South America, but also in the Caribbean and in Central America. Whereas the former species seems to be well adaptede to the archipelago and has been recorded from eight islands by five different collectors, the latter one apparently subsists but could not colonize the archipelago due to unsatisfying habitat conditions. Aphelolpium longidigitatum and A. cayanum are known from the Caribbean area and Florida. Withius piger is a cosmopolitan species and was probably introduced quite recently to the Galapagos islands by human activity.

Five species are halophiles living exclusively at the seashore and on the sea cliffs ( Paraliochthonius spp. n., Garypus granosus sp. n.). Most of the other species are recorded from various habitats from the littoral zone up to 1300 m altitude (mainly humus and litter), but are apparently adapted to the littoral zone with its adjacent habitats (mangrove litter, etc.). The presence of nearly all species in the littoral zone indicates that rafting represents an important dispersal mechanism.

Another principal natural dispersal mechanism within the archipelago might be phoresy by birds or, more reasonably, by transport of nesting material (branchlets, hay, lichens or moss). It is amazing to note that the most abundant and the most widely distributed species have been found also in or under bird nests or seabird rookeries: Galapagodinus franzi , Serianus galapagoensis , Cryptocheiridium confundens sp. n., Parachernes franzi , P. galapagensis and P. nigrimanus (but not Neocheiridium galapagoense!). Furthermore, Galapagodinus franzi was found frequently on vegetation (up to 3 or 4 meters height on Scalesia , in moss and epiphytes), which can facilitate transport in nesting material by birds. On the other hand, Lechytia chthoniiformis and Paratemnoides nidificator , which are frequently found under bark and in litter, never have been recorded in association with birds ( Turienzo et al., 2010). Both species have been recorded as phoretic on different insects (mainly Coleoptera) in Amazonia ( Aguiar & Bührnheim, 1998). Phoresy on insects seems to be a supplementary way of dispersal for Galapagodinus franzi , Serianus galapagoensis and Parachernes nigrimanus , since these species have been collected in Malaise traps, using UV light during night catches, and in flight interception traps. Paratemnoides nidificator has been caught once in a Malaise trap, as have been a few specimens of Aphelolpium cayanum and A. longidigitatum. Dispersal of species within the archipelago is influenced, too, by human activity. Agriculture has had a certain, but unquantifiable impact, either by plantations or by pastures, since on four of the five inhabited islands agriculture is practised. Unintentional introductions with agricultural goods from the mainland must also be considered ( Schatz, 1998).

The origin of the pseudoscorpion fauna of the Galapagos archipelago cannot be assessed without a “touch” of speculation, since our knowledge of the pseudoscorpion fauna of the Pacific slopes of Central and South America, particularly that of Ecuador and Colombia, is fragmentary. A close affinity with the fauna of the Caribbean area (Greater and Lesser Antilles) seems to be evident. All families and genera recorded from Galapagos are also known from the Antillean islands, besides the already mentioned Aphelolpium spp., and particularly Cryptocheiridium confundens sp. n. and even Stenolpium insulanum. This might be explained by the existence of a broad sea connection between the Caribbean region and the eastern Pacific area from 48 my ago until 3.5-3 my ago, with a sea current running from the Atlantic to the Pacific. The Panama isthmus rose some 3 my ago by uplift of the Caribbean Plate, closing the gap between the North and South American plates (see Baert, 2013). Accepting this hypothesis, A. longidigitatum, Garypus sp. and some Garypinidae ( Galapagodinus franzi , Serianus galapagoensis ) might have been among the first pseudoscorpions to arrive and colonize the archipelago. After closure of this dispersal route, some other species (e.g. some Paraliochthonius spp. , and Garypus sp. might have originated also from the Pacific coast of Mexico (Baja California) and Central America.

In accepting the Caribbean as the main origin of the present pseudoscorpion fauna of the Galapagos, it can be considered as harmonious compared to the pseudo- scorpion faunas of the adjacent regions. The (quasi) absence of some taxa is amazing, but does not invalidate this appreciation. The numer of taxa of the family Cheliferidae is decreasing in North America from north to south. It is represented by a few taxa only in the Caribbean region and it is definitely absent from South America (except for the cosmopolitan Chelifer cancroides Linnaeus, 1758). On the other hand, the family Withiidae is poorly represented by Withius piger , a cosmopolitan species. Other genera and species of this family are absent from the archipelago. This fact is puzzling, since several genera of this family (e. g. Dolichowithius Chamberlin, 1931b, Parawithius Chamberlin, 1931b and Victorwithius Feio, 1944 ) are quite diversified on the South American continent and represented also with a few species in the Caribbean area and in Central America. This absence, as that of some chernetid genera (e.g. Lustrochernes Beier, 1932 or Cordylochernes Beier, 1932) is perhaps due to either a reduced survival potentiality of those taxa during an extended period of dispersal by rafting or to the presence of a hostile environment on the Galapagos islands. Flood debris may take about 2-4 weeks to reach the islands from the South American mainland ( Thornton, 1971, cited by Schatz, 1998). Species of these genera are known to be bark-dwelling and phoretic on flying insects.