size for the tenant, neither too large nor too small.
In this box, which has cost weeks of labour, the insect has to house the
largest possible number of larvae, while allotting the necessary amount
of room to each. Method in the superposition of the floors and economy
of space are here the absolute rule.

But there is evidence of waste when the insect makes use of a bramble
hollowed by another. This is the case with Tripoxylon figulus. To obtain
the store-rooms wherein to deposit her scanty stock of Spiders, she
divides her borrowed cylinder into very unequal cells, by means of
slender clay partitions. Some are a centimetre (.39 inch.--Translator's
Note.) deep, the proper size for the insect; others are as much as two
inches. These spacious rooms, out of all proportion to the occupier,
reveal the reckless extravagance of a casual proprietress whose
title-deeds have cost her nothing.

But, whether they be the original builders or labourers touching up the
work of others, they all alike have their parasites, who constitute
the third class of bramble-dwellers. These have neither galleries to
excavate nor victuals to provide; they lay their egg in a strange cell;
and their grub feeds either on the provisions of the lawful owner's
larva or on that larva itself.

At the head of this population, as regards both the finish and the
magnitude of the structure, stands the Three-pronged Osmia (Osmia
tridentata, DUF. and PER.), to whom this chapter shall be specially
devoted. Her gallery, which has the diameter of a lead pencil, sometimes
descends to a depth of twenty inches. It is at first almost exactly
cylindrical; but, in the course of the victualling, changes occur which
modify it slightly at geometrically determined distances. The work of
boring possesses no great interest. In the month of July, we see the
insect, perched on a bramble-stump, attack the pith and dig itself a
well. When this is deep enough, the Osmia goes down, tears off a few
particles of pith and comes up again to fling her load outside. This
monotonous labour continues until the Bee deems the gallery long enough,
or until, as often happens, she finds herself stopped by an impassable
knot.

Next comes the ration of honey, the laying of the egg and the
partitioning, the last a delicate operation to which the insect proceeds
by degrees from the base to the top. At the bottom of the gallery, a
pile of honey is placed and an egg laid upon the pile; then a pa