148 THE HUMBLE-BEE VuL 
’ 
‘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.’ 
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 4. mzuscorum, which, in Shetland 
and Norway, changes to fulvous above and black underneath in sympathy 
with a similar colouring of two other species, agrorwm and helferanus, 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 4oméi 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 tiber das Artproblem. —Uber das Variieren der Hummein, 
Berlin, Part I. 1909, and Part II. 1911. 
