78 ANNALS OF SCOTTISH NATURAL HISTORY 



paludosus, F. These latter species occurred in slowly flowing 

 ditches thick with myosotis or nasturtium, etc. ; but the 

 typical running-water fauna, e.g. Hydroporus rivalis, Gyll, and 

 septentrionalis, Gyll. ; Agabus guttatus, Payk., etc., common 

 enough in Mull, did not occur at all, perhaps owing to the 

 smallness of the streams. Deronectes I 2-pustulatus, Ol., was 

 fairly common in one small stream near the south end of the 

 island, but D. depressus, F., is apparently absent. This latter 

 species is perhaps to be regarded as a lake species as well as 

 a river species, in fact the lake and river faunas are not 

 readily separable, such species as Hydroporus septentrionalis, 

 Gyll., and Platambus maculatus, L., being equally common in 

 rivers and gravelly lochs. 



With regard to this latter species, its absence from Coll 

 is perhaps not altogether attributable to the poverty of the 

 lake and river faunas. Its distribution as at present known 

 is somewhat peculiar. It does not occur in Ireland ; on 

 the west of Scotland it has so far not occurred north of 

 Dumbarton and Renfrew, while on the east it has been taken 

 in Forfar, Aberdeen S., and Easterness. It has been recorded 

 from most of the counties of England and Wales, and is 

 perhaps to be regarded as an eastern species which is 

 gradually extending its range. Its absence from Ireland 

 suggests that it is one of what Dr. Scharff 1 calls the 

 " Siberian " group, and the absence of records from the Isle 

 of Man, Arran, Mull, and Coll suggests that it had riot 

 reached the western shores of England and Scotland at the 

 time these islands were separated from the mainland. It 

 must be admitted, however, that the lists of records for the 

 Isle of Man, Arran, and Mull are at present very incomplete ! 



With regard to lake species, in spite of the number of 

 small lochs, these seemed to be very scarce, Haliplusfulvus, F. 

 and Deronectes assimilis, Payk., being the only representatives 

 I found. Loch Cliad, where there was plenty of what 



in H. discretus this marking extends much farther over the prothorax, sometimes 

 to the posterior border. In H. fubescens, again, the sternite of the last visible 

 abdominal segment is smooth and shining between the punctures, while in 

 H. discretus it is reticulately marked. 



I may also add that in H. p/anns, F. , the last abdominal sternite is marked 

 as in H. discretus, so that is a good character for separating small specimens of 

 H. planus from H. pubescens \ 



1 'The History of the European Fauna,' " Contemp. Sci. Series," 1899. 



