VII AETRACTING QUEENS 119 
The nests destroyed by the shrews and mice 
were promising ones, and I quickly set to work to 
devise means to exclude these small mammals from 
the nests that they had not yet attacked. A shrew 
is really a very small creature, and, although it looks 
much larger than a humble-bee, its skeleton being 
internal, it can squeeze through almost as small an 
aperture as a queen humble-bee, whose skeleton is 
external and unyielding. I found by experiment 
that a /apidarzus queen could comfortably pass 
through a square wooden hole measuring 3%, in. x 
zs in., and about 2 in. long, but I had so much 
difficulty in pulling a small shrew through it that I 
do not think it could possibly have managed to 
creep through by itself. Covers containing holes 
of these dimensions were therefore placed over all 
my 4apidarius nests. The cover consisted of a small 
tin lid with a large hole punched in the middle. 
Over the hole were fixed two strips of wood, one 
on either side of the hole, one of the strips being 
fixed to the tin, and the other strip being connected 
to the first strip by a pair of screws, which made it 
possible to vary to a nicety the size of the aperture 
between them, small blocks of wood of the width 
of the aperture required being placed between the 
strips, inside the screws. These covers were pressed 
into the ground over the mouths of the tunnels lead- 
ing to the nests. The queens showed great intelli- 
gence in quickly recognising the holes in the covers, 
and seemed to enjoy passing through the narrow 
apertures. Unfortunately the queens at first hada 
