178 

THE COMITY OF SPIDERS 

certain that the present distribution is of much more recent occurrence. 

Hypothetical land bridges, it seems to me, have sometimes been 

suggested to explain facts of distribution which have puzzled 

zoologists who have not credited invertebrates with sufficient powers 

of dispersal, and who have not realized their intolerance of even quite 

small differences in environmental conditions. It is interesting to 

reverse the process by inventing islands in order to see what 

conclusions the ardent protagonists of land bridges might draw from 

the resulting faunas! Were the sea to encroach eastwards from the 

Severn estuary and to follow the course of the Thames across England 

to the Thames estuary the southern part of England would be 

converted into an island. In this relatively small island we should have 

no less than 54 spiders absent from the mainland of England, Wales 

and Scotland. Since most of these species occur in France there might 

be a temptation to suggest a land connection with that country more 

recent than with England if we did not know the history of the 

severance! These species are: 

Eresus niger 

Pet., 

Dictyna puella 

Sim.,

  D

.

 viridissima 

Walck., 

Lathys stigmatisata 

Menge., 

Uloborus walckenaerius 

Latr., 

Scytodes 

thoracica 

Latr., 

Segestria bavarica 

C.L.K.,

 Drassodes minor 

Camb., 

Phaeocedus braccatus 

L.K., 

Zelotes pedestris 

C.L.K.,

 Gnaphosa 

occidentalis 

Sim., 

Micaria scintillans 

Camb., 

Cheiracanthium

,

 pennyi 

Camb., 

Agroeca pullata 

Thor., 

A

.

 lusatica 

L.K.,

 Agraecina striata 

Kulcz.,

 Phrurolithus minimus 

C.L.K.,

 Pistius truncatus 

Pall., 

Xysticus 

robustus 

Hahn., X. 

luctator 

L.K.,

 Oxyptila nigrita 

Thor., 

Philodromus 

levipes 

Linn., 

Thanatus formicinus 

Oliv., 

Salticus zebraneus 

C.L.K.,

Heliophanus expers 

Camb., 

Euophrys molesta 

Camb., 

E

.

 lanigera 

Sim., 

Sitticus zimmermanni 

Sim., 

Phlegra fasciata

,

Hahn., 

Pellenes 

tripunctatus 

Walck., 

Oxyopes heterophthalmus 

Latr., 

Lycosa 

paludicola 

Walck., 

Tarentula fabrilis 

Walck., 

Xerolycosa nemoralis 

Westr., 

Aulonia albimana 

Walck., 

Cryphoeca moerens 

[?

maerens

]

Camb., 

Aranea inconspicua 

Sim.,

 A

.

 alpica

 L.K.,

 A

.

 angulata