Clare Island Survey — Acarinida. 39 11 



Sub-fam. Hydryphantinae. 

 Hydryphantes ruber (de Geer). 



Common in bog-pools on Cartron mountain, near Letterfrack, March, 1904 

 (S. W. Kemp). 



A few specimens with a somewhat longer eye-plate approaching the variety 

 prolongatus, Piersig, occurred with the type-form in this locality. In these 

 specimens the eye-plate measures about '410 mm. along the middle line, by 

 407 in breadth, so that it falls short of Piersig's description, which gives '6 mm. 

 as the length of the eye-plate in prolongatus. Mr. Williamson has recorded the 

 variety from Scotland (36). 



Thyas longirostris, Piersig. 



An example of this fine species was collected by Mr. W. F. de Vismes Kane 

 in Ballynahinch Lake, Connemara, June, 1900. 



I first met with this species at Kenmare, in the south-west of Ireland, 

 where some extremely large specimens, nearly 3 mm. in length, occurred in a 

 small pool full of Callitriche in the month of April. It has also been found 

 in the county Dublin, and in Donegal (Bundoran). 



Mr. Soar has recorded it from the Norfolk Broads, and Mr. Williamson 

 met with it in the Island of Tiree, Scotland (40). 



Distribution. — Germany (Koeuike) ; Sweden (Piersig) ; Switzerland, 

 Gotland, and Belgium (Walter); British Isles. 



Thyas vigilans Piersig. 



An adult specimen of this species was found in a Sphagnum-pool near 

 Louisburgh in July, while the nymph occurred amongst moss on the edge of a 

 small stream on Clare Island. 



These are the first specimens of this interesting species that have been 

 found in Ireland. The characteristic chitinous plate surrounding the pigmented 

 median eye is well developed in the nymph. 



The provisional genital area carries four rather large paired discs, 

 separated by an oblong chitinous structure, which appears to be partly 

 subcutaneous. Three long, stout bristles spring from the front margin and 

 extend backwards across the genital field. 



Thyas vigilans seems to affect pools containing Sphagnum, and the German 

 specimens occurred in a very similar habitat (18, p. 399). According to Piersig 

 the larvae of this mite are parasitic on gnats. 



Distribution. — Germany (Koeuike) ; England (Soar); Ireland. 



B2 



