82 ANNALS OF SCOTTISH NATURAL HISTORY 



Lennon's collection are all H. niorio, Dey. There are, 

 however, 3 specimens of celatus in the collection which were 

 labelled niorio. 



With regard to Agabus biguttatus, Ol., there is room for 

 comment. 



In his collection Lerinon has I 8 specimens representing 

 this species, all of which were A. guttatus, Payk ; while 

 among 1 5 specimens representing A. guttatus, and all 

 registered " Mid-Solway," were 3 specimens of A. biguttatus. 

 In his MS. List Lennon says of A. biguttatus that it is " local 

 but not uncommon in small clear-running streams," while in 

 " Some Addits. to the Scott. Coll.," 1892, written jointly by 

 him and Mr. W. Robinson Douglas, the species is described 

 as "common, Orchardton, W. D.R. D." Mr. Robinson 

 Douglas very kindly allowed me to examine the water- 

 beetles in his collection, and all his so-called A. biguttatus 

 turned out to be A. guttatus ! The two species are, I think, 

 often mixed by collectors, and I think that a number of the 

 records of biguttatus really refer to guttatus. The late Mr. 

 Arthur Chitty allowed me to examine the specimens which 

 he took at Loch Awe and at Forres, and recorded as A. 

 biguttatus ("EMM.," ser. 2, iii. 216, 1892 ; " Ann. Scott. Nat. 

 Hist," ii. i 19, 1893 ; and "EMM.," ser. 2, iv. 68-71, 1893), 

 and they were all A. guttatus, Payk. 



The species is really easily distinguished from guttatus by 

 several characters. First in the c? of biguttatus the anterior 

 claw of the anterior tarsi is toothed, while in guttatus there 

 is no tooth. Secondly, the palpi are usually pitchy in 

 biguttatus, and usually testaceous \\~\guttatus, but this is not an 

 altogether reliable character as occasionally guttatus has 

 rather dark palpi. If, however, the elytra are examined 

 under a high-power lens a difference between the two species 

 is quite evident. In biguttatus the surface is smooth and finely 

 reticulate without any punctures in the reticulation, while 

 in guttatus, where the lines of the reticulation cross one another 

 there is a puncture. Thus guttatus is reticulate and punc- 

 tate while biguttatus is reticulate and impunctate ! Some- 

 times the punctuation of guttatus is so well marked that the 

 specimen appears punctate even under low magnification, 

 e.g., some of the specimens in the Power Collection but as 



