AND RENA. 
207 
former depending upon both the quantity and quality 
of the food stored up, for tlie pollen of different plants 
varies possibly in its amount of nutriment, else why 
should we observe so marked a difference in the sizes 
of individuals whose parent instinct would prompt to 
furnish them with an uniform and equal supply. The 
differences of specific appearance is often very consider¬ 
able in long genera, and perhaps in no genus is it 
more conspicuously so than in Andrena , for here we 
have some wholly covered with dense hair, and others 
almost glabrous; others again with the thorax only 
pubescent; some are black, some white, some fulvous, 
or golden tinted, and some red; some we find banded 
with decumbent down, and others with merely lateral 
spots of this close hair, but the most prevalent colour 
is brown, which will sometimes by immaturity take a 
fulvous or reddish hue. In many males we see excen- 
trically large transversely square heads broader than the 
thorax, which also have widely spreading forcipate man¬ 
dibles, with often a downward projecting spine at their 
base beneath; and it is chiefly these extravagantly 
formed males which are most dissimilar to their own 
partners that the result of observation alone confirms 
their specific identity. In other cases the males are so 
like their females that a mere neophyte would unite them. 
In many males the clypeus and labrum are white, which 
also occurs in some females; for instance, in A. labialis, 
but tins peculiarity is found more rarely in this sex. 
The species are much exposed to the restricting in¬ 
fluences of several parasites, whose parasitism is of a 
varying character, but the term should properly be ap¬ 
plied only to the bees which deposit their eggs in their 
nests, and whose young, like that of the cuckoo among 
