The Colcoptcrist in Ireland. 143 



hills, might suggest a common origin; hnV bnc?inca does not 

 differ in structure at all from afrata, while this s^tbivtundata 

 does. Of course, we all know how difficult — nay, impossible, 

 it is, accurately to define what we mean by " a species," and 

 whether we call any particular form a species, or a racial 

 variety matters but little; the really interesting point about 

 this oily-looking light-brown St/pha, which lies kicking in 

 our laurel bottle, is, that the form is almost exclusively re- 

 stricted to Ireland and the Isle of Man. There are a few, 

 possibly doubtful, English records, as the form brunnea might 

 easil}^ have been mistaken for it; whether the type-form has 

 ever been taken in Ireland we cannot say,' but if it had never 

 been discovered, that is no proof that it does not exist there ; 

 but whether it exists or not, roughly speaking, 5*. atrata is 

 the English, and 5*. subrotttndata, the Irish form, and the 

 question at once arises — w^hy should this be? Has the insect 

 been differentiated since the complete disruption of Ireland 

 from Great Britain ? or was S. S7cbjvt7tndata the original form 

 which in England has been supplanted, and, indeed, extermi- 

 nated by a younger rival, 5^. atrata ? And where does our 

 mountain kS. britujiea come in? Can that be older than either 

 of the other two, or have all three been synchronously diffe- 

 rentiated? Such are some of the problems which this small 

 beetle suggests. It may possibly also occur to us that this 

 insect is rather a stumbling-block in the way of current 

 theories of melanism. Upland forms being presumably relics 

 of the age of the passing glaciers, ought according to such 

 theories to be black, or at least, darker than exclusively low- 

 land forms; and many Geodephaga, such as Carabtis arvcfisis, 

 Notiophilus aquaticus and N. palustris, and Calathus melano- 

 cephalus, by their melanic alpine variation are consistent 

 evidences of such a principle, but here we have a beetle whose 

 lowdand form is black, and upland {briinnca^ form pale! Such 

 questions as these can only be answered by careful record of 

 the occurrence of the particular species we may be investi- 

 gating, its varieties, and allied species, over the whole Palae- 

 arctic zone, and such records seem at present too fragmentary 

 and indefinite to be of much service, while such as do exist 



^ Both Silpha atrata (type), and its variety hrunnca, occur in Ireland, It 

 is worth}' of remark that S. siibrotundala, though generally brown, is sonie- 

 thnes black. — Eds. 



