228 The Irish Naturalut. [Sept., 



dark in colour, the yellow bands tending to become narrow 

 and broken up. The nearest ally of Z'. herbigrada is P. palustris^ 

 L,., an abundant spider in which the cephalothorax is mostly 

 of a black-brown colour, showing three narrow yellow bands, 

 the central drawn out to a fine point in front. But in the 

 specimen of P. palustris taken at Clonbrock the central band is 

 somewhat widened behind the eyes. This form I have received 

 from several Irish localities and the series goes far to bridge 

 the gap between typical P. palustris and P. herbigrada. In 

 the females of both these species the epigyne is very large 

 and of a truncated triangular form. This structure in these 

 and allied species has recently been carefully described and 

 figured by Rev. F. Pickard- Cambridge^. In P. herbigrada it is 

 relatively larger and more prominent than in P. palicstris, but 

 it varies somewhat in different individuals of the same species, 

 andi'in tile present specimen the hind corners are extremely 

 prominent and rugose (fig. 3). 



'It is of interest to note that in some of the dusky species 

 6uch as P. amentata, CI., and P. agricola, Thor., the yellow 

 colour is predominant in the cephalothorax of very young 

 specimens ; as the spider grows older, the amount of dark 

 colour in the pattern increases. This suggests that/^. herbigrada^ 

 with its broad expanse of yellow when adult, represents an 

 old stage in the evolution of the genus, a suggCvStion supported 

 by the rarity and discontinuous range of the species. While 

 its dark-hued relation P. palustris is spread abundantly over 

 our islands, and is found on the Continent from I^apland to 

 Italy, P. herbigrada is apparently absent from the greater 

 part of Central Europe, and almost restricted to northern and 

 western regions in Scandinavia, Britain and Ireland. It 

 would seem, therefore, that P. palustris is the younger and 

 more vigorous species, and has largely superseded P. herbigrada 

 in the struggle for existence. The problem remains whether 

 the darkening of the cephalothoracic pattern has been itself 

 an advantageous factor in the conflict, or whether it is but 

 the necessary accompaniment of other and deeper causes. 



^ Amu Mag, Nat. Hist. (6), vol. xv., 1895 (p. 34, pi. iv.) 



