to require the solid support of a rock, into an aerial dwelling. A
hedge-shrub of any kind whatever--hawthorn, pomegranate, Christ's
thorn--provides her with a foundation, usually as high as a man's
head. The holm-oak and the elm give her a greater altitude. She
chooses in the bushy clump a twig no thicker than a straw; and on this
narrow base she constructs her edifice with the same mortar that she
would employ under a balcony or the ledge of a roof. When finished,
the nest is a ball of earth, bisected by the twig. It is the size of
an apricot when the work of a single insect and of one's fist if
several have collaborated; but this latter case is rare.

Both Bees use the same materials: calcareous clay, mingled with a
little sand and kneaded into a paste with the mason's own saliva. Damp
places, which would facilitate the quarrying and reduce the
expenditure of saliva for mixing the mortar, are scorned by the Mason-
bees, who refuse fresh earth for building even as our own builders
refuse plaster and lime that have long lost their setting-properties.
These materials, when soaked with pure moisture, would not hold
properly. What is wanted is a dry dust, which greedily absorbs the
disgorged saliva and forms with the latter's albuminous elements a
sort of readily-hardening Roman cement, something in short resembling
the cement which we obtain with quicklime and white of egg.

The mortar-quarry which the Sicilian Mason-bee prefers to work is a
frequented highway, whose metal of chalky flints, crushed by the
passing wheels, has become a smooth surface, like a continuous
flagstone. Whether settling on a twig in a hedge or fixing her abode
under the eaves of some rural dwelling, she always goes for her
building-materials to the nearest path or road, without allowing
herself to be distracted from her business by the constant traffic of