148 THE HUMBLE-BEE 



"light specimens " and "dark specimens" of many 

 of the species, but these expressions must not be 

 taken too literally, for individuals are sometimes 

 found in which the degree of melanism is greater 

 in one part of the body than in another part. 



The difficulty in naming specimens from the 

 colour-patterns of their coats is increased by the 

 fact that certain species resemble one another very 

 closely. But careful inspection generally reveals at 

 least slight differences in the extent and tint of the 

 colours, and in their manner of encroaching upon 

 one another. 1 



Another source of perplexity to the beginner 

 arises from the liability of the colours to fade and 

 bleach from long exposure to sunlight, bright red 

 changing to rust-red, and orange, yellow, and white 

 to pale brown or dingy white : black even loses 



1 An important factor in the variation in the coat colour of the humble-bees 

 is regional convergence, namely, the tendency of different species to show a 

 parallel variation in the same region. Thus Britain is within a large region 

 of melanism, extending into-the Alps but not into the Pyrenees, which shows 

 itself most strongly in Schleswig-Holstein, Denmark, and Southern Scandinavia, 

 and is more marked in the south of England than in Scotland and Ireland. 

 Another kind of regional convergence is seen in B. muscorum, which, in Shetland 

 and Norway, changes to fulvous above and black underneath in sympathy 

 with a similar colouring of two other species, agrorutn and helferamis, in 

 Norway. A remarkable instance of convergence is found in the Caucasian 

 Mountains where the yellow bands of most of the species become white. In 

 connection with these cases it is interesting to note that most of the North 

 American Bonibi conform to a particular colour scheme, namely, greenish- 

 yellow, with a black tail and usually a black band on the thorax. 



A further feature in the variation of humble-bees, not very noticeable within 

 the limits of the United Kingdom, is that the queens as a rule show greater 

 variation than the males ; in certain regions the queens of certain species 

 acquire a peculiar coloration while their males show little or no change from 

 the type. 



See Dr. O. Vogt's recent work on variation in European and Western Asiatic 

 humble-bees, Studien iiber das Artproblem. Oder das Variieren der Hunimcln, 

 Berlin, Part I. 1909, and Part II. 191 1. 



