s are used
in making the putty; probably each species has its own preferences and
its little professional secrets; but hitherto observation has taught me
nothing concerning these details. Whatever worker prepare it, the putty
is very much the same in appearance. When fresh, it is always a clear
dark green. Later, especially in the parts exposed to the air, it
changes, no doubt through fermentation, to the colour of dead leaves,
to brown, to dull-yellow; and the leafy character of its origin is no
longer apparent. But uniformity in the materials employed must not
lead us to believe in uniformity in the lodging; on the contrary, this
lodging varies greatly with the different species, though there is a
marked predilection in favour of empty shells. Thus Latreille's Osmia,
together with the Three-horned Osmia, uses the spacious structures
of the Mason-bee of the Sheds; she likes the magnificent cells of the
Masked Anthophora; and she is always ready to establish herself in the
cylinder of any reed lying flat on the ground.

I have already spoken of an Osmia (O. cyanoxantha, PEREZ) who elects
to make her home in the old nests of the Mason-bee of the Pebbles. (Cf.
"The Mason-bees": chapter 10.--Translator's Note.) Her closing-plug is
made of a stout concrete, consisting of fair-sized bits of gravel
sunk in the green paste; but for the inner partitions she employs
only unalloyed putty. As the outer door, situated on the curve of an
unprotected dome, is exposed to the inclemencies of the weather,
the mother has to think of fortifying it. Danger, no doubt, is the
originator of that gritty concrete.

The Golden Osmia (O. aurulenta, LATR.) absolutely insists on an empty
Snail-shell as her residence. The Brown or Girdled Snail, the Garden
Snail and especially the Common Snail, who has a more spacious spiral,
all scattered at random in the grass, at the foot of the walls and of
the sun-swept rocks, furnish her with her usual dwelling-house. Her
dried putty is a kind of felt full of short white hairs. It must come
from some hairy-leaved plant, one of the Boragineae perhaps, rich both
in mucilage and the necessary bristles.

The Red Osmia (O. rufo-hirta, LATR.) has a weakness for the Brown Snail
and the Garden Snail, in whose shells I find her taking refuge in April
when the north-wind blows. I am not yet much acquainted with her work,
which should resemble that of the Golden Osmia.

The Green Osmia (O. viridana, MORAWITZ) takes u