Why this nice finish, if the builder be wholly absorbed in the solidity of her work?
Here is another detail: among the bits of gravel employed for the outer covering of the cupola, grains of quartz predominate.

They are polished and translucent; they glitter slightly and please the eye.

Why are these little pebbles preferred to chips of lime-stone, when both materials are found in equal abundance around the nest?
A yet more remarkable feature: we find pretty often, encrusted on the dome, a few tiny, empty snail-shells, bleached by the sun.

The species usually selected by the Eumenes is one of the smaller Helices--Helix strigata--frequent on our parched slopes.

I have seen nests where this Helix took the place of pebbles almost entirely.