Junk, 1889. 
WILD BEES. 
125 
WILD BEES. 
BY R. C. L. PERKINS, 
JESUS COLLEGE, OXFORD. 
(Continued from page 116 .) 
Andrena. 
This is the most extensive of our British genera, compris¬ 
ing no less than forty-eight distinct species, and, therefore, 
there is naturally great diversity of appearance between many 
of them. They are of simple habits and universal distribution, 
and many are amongst the commonest of our wild bees. 
They form cylindrical burrows in the ground, some species 
preferring bare spots, others grassy banks ; some will make 
their nests in pathways so liard-trodden that no one would 
imagine it possible for any bee to pierce the soil, others are 
partial to loose sand or the finely-sifted soil of a garden flower¬ 
bed, while others again will burrow in the stiffest clay. These 
burrows are just of sufficient size to admit the maker, and 
reach usually to a depth of from about five to nine inches. 
Most of the species form “colonies” of greater or less 
extent. Sometimes they are so large that a space of some 
yards will be riddled with burrows almost touching one 
another ; yet there is no division of labour amongst the 
individuals of the colony, such as we see in the social bees, 
but each keeps to its own nidus and takes no notice of its 
neighbours. 
The cause of this gregarious habit is obscure: it may 
have originated from need of protection. Certain enemies 
may be intimidated by the numbers which are always to be 
seen round a vigorous colony. At any rate, in the case of 
Anthophora , another genus which forms huge colonies, this 
is probably the case, and I know that many people unacquainted 
with these bees would hesitate before approaching very close 
to one of the enormously populous colonies of Anthophora 
acervorum. 
On the other hand, I have already mentioned the ravages 
of the Forjiculce, to which colonies are especially exposed, 
and, similarly, insectivorous birds not unfrequently pay them 
visits. 
There is some reason to think that in some cases at any 
rate the sole cause of such colonies lies in the fact that the 
