28 The Irish Naturalist. February, 



ON A SPIDER NEW TO SCIENCE 

 RECENTLY FOUND IN IRELAND. 



BY A. RANDELL JACKSON, M.B., D.SC. 

 [Plate I.]. 



Erigone Welciiii sp. nov. 



Several examples of this spider were sent to me by Mr. 

 D. R. Pack-Beresford in the autumn of 1910. These appeared 

 to us to belong to an undescribed species. I submitted the 

 specimens to the Rev. O. Pickard-Cambridge, and to 

 Professor Kulczynski, both of whom confirmed our 

 opinion. In the male sex this spider is very distinct from 

 all the other British species of Erigone. The female, 

 however, as is usual in this genus, is not very strikingly 

 different from its congeners, but if the two examples we 

 possess are typical, the structure of the vulva would, I think, 

 enable the species to be recognised without very much 

 difficulty. This organ, however, is subject to a good deal 

 of variation, and possibly the determination of the females 

 of this species may always be difficult. 



The cephalothorax of the male measures 1.45 mm. in 

 length, it is of a dark reddish-brown colour, almost black 

 in fact. The femora and subsequent joints of the legs and 

 palpi are clear yellow-brown, whilst the fakes and coxae 

 are of an intermediate hue. The sternum and maxillae are 

 dark reddish-brown, the latter, as is usual in the genus, 

 being studded in the male sex with numerous large nipple- 

 shaped prominences, each bearing a bristle. In the females 

 these are less numerous, and a good deal smaller. 



The ABDOMEN is of a pale dingy brown colour. 



The facies of the male is very like that of the other 

 members of the genus. The palpal differences can, however, 

 easily be made out with a pocket lens, and I think that 

 a little practice would enable the species to be recognised 

 with the naked eye. 



The FALCES of the male bear on their external borders 

 a series of seven very strong teeth. Some of these, at any 

 rate, bear rather short hairs. The teeth are very much 

 stronger than those found in a similar position in the other 

 British members of the genus, with one exception. 



