Clare Island Survey. 



35 

 ARANEIDA. 



By DENIS E. PACK BEBESFOED, B.A. 



Read November 13. Published December 8, 1911. 



INTBODUCTION. 



When studying the geographical distribution of spiders, we must bear in 

 mind that, although they have no wings, their means of dispersal are almost, 

 if not quite, as great as if they had ; for most species are aeronauts in their 

 youth, while many of the smaller species are probably carried about by the 

 wind at all times. The question then what species of spiders we are likely 

 to find in any given area resolves itself very much into a question of suitable 

 habitat, or what kinds are likely to survive and increase under the conditions 

 in which they may find themselves. Thus on cliffs exposed to the Atlantic 

 storms, only the hardiest of species, such as Segestria senoeulata and Textrix 

 denticulata, which live amongst stones and in crannies in the rocks, can sur- 

 vive. Both these species are present in enormous numbers on the cliffs in 

 the far west of Clare Island. Then in sheltered nooks facing south or west 

 we find species such as Dysdera crocota and Heliophanus cupreics, which usually 

 inhabit warmer localities, while again on the mountain-tops we find species 

 like Tmeticus prvdens, which, in this country at all events, seems to be 

 confined almost exclusively to such places. 



Again, we are met with the difficulty that such a small amount of work 

 has yet been done at spiders, that we know but little of the life-histories and 

 general distribution of any but the commonest species. Thus, though some 

 kinds are met with nearly everywhere in suitable habitats, many species are 

 extraordinarily local, so that though quite numerous in a very limited area, 

 they disappear entirely outside it, to reappear in another colony elsewhere. 

 Others, especially in the male sex, are very short-lived, and are only found in 

 the adult stage, in which alone it is possible to identify them with any 

 certainty, for very short seasons of the year ; consequently it is evident that 

 in order to make anything like a complete survey of the species inhabiting 

 any given area, it would be necessary to live and collect in that area, not only 

 all the year round, but for many years in succession. 



Work of this sort being manifestly impossible in a locality such as Clare 

 Island, all one can hope to do is to give a list of the species which are to be 

 K.I. A, PBOC, vol. xxxi. A 35 



