VIII 



i 5 o THE HUMBLE-BEE 



munities, and, in three of the cases, is of a larger 

 size than the northern form. 



The relationship between B. terrestris and B. 

 hicorum, and that between B. rtideratus and B. 

 Jwrtorum are closer than in the cases of the other 

 two couples ; but although these four forms are 

 abundant over the greater part of the kingdom, 

 living side by side, terrestris rarely if ever inter- 

 breeds with lucorum, and ruderatus with hortorum, 

 for intermediate specimens are seldom found, and 

 I have never known both forms to be produced by 

 the same queen. In each case there is evidently 

 a barrier between the two forms that does not 

 exist ; for instance, between the English and Italian 

 races of the honey-bee which, when brought to- 

 gether, cross freely, and it seems best to regard 

 them as distinct but closely-allied species. 



Between a slight differentiation, such as that which 

 separates B. terrestris from B. lucorum, and the 

 deep divisions that part well-marked species, all 

 degrees of relationship occur. B. latreillellus and 

 B. distinguendus are almost as closely related to 

 one another as terrestris and lucorum ; the differ- 

 ences between B. pratorum, B. jonellus, and B. 

 lapponicus are slightly deeper, and those between 

 B. derhamellus and B. sylvarum deeper still : in 

 the last case decided differences in the shape of 

 the armature appear for the first time. 



In Shetland, large-sized varieties of B. jonellus 

 and B. muscorum, having the coat longer and more 

 deeply coloured than it is in the mainland forms, 



