THE DISPERSAL OF SPIDERS 
179
Linn., 
Theridiosoma gemmosum 
L.K.,
 Theridion pulchellum 
Walck., 
Dipoena melanogaster 
C.L.K.,
  D
.
 prona 
Menge., 
D
.
 tristis 
Hahn., 
Enoplognatha schaufussi 
L.K.,
 Anacotyle stativa 
Sim., 
Lophocarenum 
stramineum 
Menge, 
Hybocoptus decollatus 
Sim., 
Colobocyba mitis 
Camb., 
Trichoncus saxicolus 
Camb., 
T
.
 affinis 
Kulcz., 
Acartauchenius 
scurrilis 
Camb., 
Porrhomma oblitum 
Camb., 
Centromerus subacutus 
Camb. 
We need have little doubt that temperature is the main factor 
restricting these species to this small area of England. 
Now the sea is not the only element which creates isolation. We 
have species which are restricted to particular habitats, such as 
mountain tops, caves, sandhills, marshes and ants
'
 nests. It has been 
suggested that the mountain species retreated to high altitudes from 
the plains they inhabited when the Ice Age was waning, but there has 
never been an age of caves, of sandhills, of marsh or of ants! The 
inhabitants of these  islands  have had to colonize them across 
inhospitable areas in which they could not survive, and it cannot be 
suggested that man assisted them in this feat. Faced with this difficulty 
Berland is now prepared to concede that spiders can disperse 
themselves short distances by air, so our views are drawing nearer. I 
go further, and explain, for instance, the distribution of such species as 
Coryphaeolanus holmgreni
,
 Erigone tirolensis
,
 Hilaira frigida 
and 
Meioneta nigripes 
on many suitable mountain tops and on isolated 
Arctic islands, such as Jan Mayen, Bear Island and Spitzbergen, as 
being due to their powers of dispersal by air. These islands can have 
had no spider fauna during the last Ice Age, and when the ice retreated 
there was no land bridge connecting them to a mainland. As for their 
colonization of mountain tops, let us not forget the frequent discovery 
of numerous invertebrates on their snowy slopes, invertebrates which 
have been carried downward (as if there were some magnetic force 
directing them thither) in the downward air currents which airmen so 
frequently experience over mountains. 





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