232 PROCEEDINGS OF THE 



Europe possesses nine species, six of which are found in Britain. 

 In nearly all the species the females may be distinguished from 

 the males, by the elytra of the former being deeply sulcated, while 

 those of the males are smooth. Another distinction which char- 

 acterises the males of Dytiscus, and the three allied genera, 

 CyUster, Hydaticus, and A dims, is the curious patellated foiTa 

 of the anterior tarsi, the three upper joints being expanded into 

 a circular disc, on which are placed a number of suckers by which 

 the creatures are enabled to attach themselves to smooth surfaces. 



In Scotland there occurs in our ditches, besides marginalis, 

 another species, jyimdidatus, easily recognisable by its deep black 

 hue both above and below, by the three distinct rows of punc- 

 tures on the elytra, and by the rounded form of the hinder 

 coxae. Scotland possesses yet another species, Dytiscus Lapponicus. 

 It was first discovered in 1854 by the Rev. H. Clark, who 

 obtained, with much difficulty, four specimens from a loch in the 

 island of Mull. The species may easily be distinguished from 

 marginalis. and indeed from all others, by its diminutive size, by 

 its slender and elongated form, by its yellow scutellum, by the 

 very acute form of the hinder coxae, but chiefly by the great 

 number of faint yellow lines on the elytra, each elytron bearing 

 from eighteen to twenty of these. These lines are not so apparent 

 in the dried specimens, but they are quite remarkable when 

 observed while the creature is under water. They appear as if 

 shining through from the under side of the somewhat transparent 

 wing-cases. Mr Hislop of Polmont, one of our honorary mem- 

 bers, was the second to take the insect. He obtained a few speci- 

 mens also in Mull. 



In 1859, while on a tour through the south of the same island, 

 my brother and I took fifteen specimens in a very small tarn, 

 after a long and unsuccessful hunt in many mountain lakes. 



Again, in 1866, happening to be at Tobermory, in the north of 

 Mull, I made a careful search of all the lakes in the neighbour- 

 hood, and that is saying not a little, but was quite unsuccessful. 

 The last night of my stay in the island, I recollected having seen 

 from a considerable distance Avhat appeared to be a small tarn, 

 and which I had not yet searched. Unwilling to give up while 

 any hope remained, I started oft', and on reaching the place found 

 a lake different from any I had yet visited. It was situated on 

 the top of a curiously shaped hill, standing somewhat alone. The 



