Clare Island Survey — Aquatic Coleoptera. 29 13 



With regard to the water-beetles of West Mayo as a whole, they include 

 species showing very different ranges of distribution in Ireland. Most of 

 them show no particular localisation ; a smaller number are marginal in their 

 distribution, being almost or entirely confined to the coastal counties while a 

 very few are remarkable chiefly in that they are absent from the centre and 

 east of Ireland. Some of these latter are found in the north and west, others 

 in the south and west, none apparently being common to north, west and 

 south. 



This " western " group consists of only eight species but if we include a 

 few which, although not so far found in West Mayo, occur in one of the 

 neighbouring western counties, it consists of thirteen species which are as 

 follows : — 



West and North Species. West and South Species. 



N. Caelambus ix-lineatus, Steph. S. Copelatus agilis, F. 



N. Deronectes griseo-striatus, Be G. S. and W. Paracymus nigro-aeneus, 



S. Hydroporus dorsalis, F. Sahib. 



X. H. melanarius, Sturm. S. Helochares punctatus, Sharp. 



N. Agabus unguicularis, Thorns. S. Lacoobius ytenensis, Sharp. 



N. A. congener, Payk. S. L. regularis, Bey. 



K Dytiscus lapponicus, Gyll. S. Hydraena testacea, Curt. 



The accompanying " symbol "-maps illustrate the distribution of these two 

 groups : — ■ 



WD ED ld AN WD ED LD AN 



FE TY AR DO FE TY AE D0 



WMSL LE WO WMSL le mo 



EM RO CV LH EM EO CV LH 



WG NG LF WHME WC NG LF WHME 



SG EC KD DU SG KC KD DU 



CL NT QC CW WI CL NT QC CW Wl 



NK LK ST KK WX NK LK ST RK WX 



SK MC EC WA SK MC EC WA 



wc WC 



Fig. 1.— West and North Group. Fig. 2.— West and South Group. 



With regard to their British distribution, six of these species may be 

 described as belonging to the " Scottish " and " Highland " types— marked N. 

 in above list— and six apparently belong to the " English " type— marked S. 



