The Scottish Naturalist. 341 



species only are common to all the three groups of islands. 

 Orkney has 77 species that have not yet been detected in Shet- 

 land or the Outer Hebrides; while Shetland has 14, and the 

 Outer Hebrides 23 species not found in the other islands. To 

 Orkney and Shetland 21 species are common which have not 

 been seen in the Outer Hebrides ; while the latter group and 

 Orkney have in common 15 species not in Shetland. On the 

 other hand, Shetland and the Outer Hebrides have no species in 

 common that are not also in Orkney. It is extremely likely that 

 further investigation will add more or less to the number of 

 species in each group — probably adding considerably to the 

 number of Hebridean species — but at the same time it is pos- 

 sible that the relative proportions will not be very greatly 

 disturbed. 



Before proceeding to inquire into the origin of the fauna of 

 each of the groups, it will be desirable to glance at some pecu- 

 liarities presented by many of the species, as indicated by Mr 

 Jenner Weir in the papers already cited. 



Hepialus humuli. — In Shetland the very peculiar form, Hcth- 

 landka Stgr., in which the male, instead of having immaculate 

 silvery-white wings, shows a greater or less tendency to assume 

 the very different coloration of the female, is not uncommon, 

 but ordinary-coloured males also occur. In Orkney and the 

 Hebrides the male is of the normal colour. The females are 

 normal in all the groups of islands. 



Cheloiiia plantagitiis. — Both in Shetland and Orkney there is 

 a tendency to have the upper wings marked with pale yellow, 

 and the lower wings a dark yellow. 



Dasypolia te?)ipli. — A light variety occurs in Shetland, as also 

 a darker variety. 



Noctua /estiva, JV. Dah/ii, and A r . rtibi, are in Orkney very 

 similar, the prevailing colour being a ruddy brown. 



DiaHthcecia conspersa. — In Shetland much darker than usual. 



Aplecta occulta. — In Shetland this is pale like the southern 

 type, and not dark as in the Scottish Highlands. 



Anarta mclanopa. — In Shetland the front wings are yellower 

 than in Rannoch examples. 



Boar?nia repandata presents in the Outer Hebrides a well- 

 defined local variety (sodorenshnn), in which the wings (especially 

 in the female) are leaden grey with darker markings, but with 

 little or no trace of brown. 



Dasydia obfuscata. — In the Outer Hebrides lighter than usual. 



