The Eumenes' cupola is the work of an artist; and the artist would be sorry to cover his masterpiece with whitewash. I crave forgiveness for a suggestion which I advance with all the reserve befitting so delicate a subject. Would it not be possible for the cromlech-builder to take a pride in her work, to look upon it with some affection and to feel gratified by this evidence of her cleverness? Might there not be an insect science of aesthetics? I seem at least to catch a glimpse, in the Eumenes, of a propensity to beautify her work. The nest must be, before all, a solid habitation, an inviolable stronghold; but, should ornament intervene without jeopardizing the power of resistance, will the worker remain indifferent to it? Who would say?
Let us set forth the facts. The orifice at the top, if left as a mere hole, would suit the purpose quite as well as an elaborate door: the insect would lose nothing in regard to facilities for coming and going and would gain by shortening the labour. Yet we find, on the contrary, the mouth of an amphora, gracefully curved, worthy of a potter's wheel. A choice cement and careful work are necessary for the confection of its slender, funnelled shaft. 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. They were like boxes made of shells, the work of a patient hand.
A comparison offers here. Certain Australian birds, notably the Bower-birds, build themselves covered walks, or playhouses, with interwoven twigs, and decorate the two entrances to the portico by strewing the threshold with anything that they can find in the shape of glittering, polished, or bright-coloured objects. Every door-sill is a cabinet of curiosities where the collector gathers smooth pebbles, variegated shells, empty snail-shells, parrot's feathers, bones that have come to look like sticks of ivory. The odds and ends mislaid by man find a home in the bird's museum, where we see pipe-stems, metal buttons, strips of cotton stuff and stone axe-heads.
The collection at either entrance to the bower is large enough to fill half a bushel. As these objects are of no use to the bird, its only motive for accumulating them must be an art-lover's hobby. Our common Magpie has similar tastes: any shiny thing that he comes upon he picks up, hides and hoards.
Well, the Eumenes, who shares this passion for bright pebbles and empty snail-shells, is the Bower-bird of the insect world; but she is a more practical collector, knows how to combine the useful and the ornamental and employs her finds in the construction of her nest, which is both a fortress and a museum. When she finds nodules of translucent quartz, she rejects everything else: the building will be all the prettier for them. When she comes across a little white shell, she hastens to beautify her dome with it; should fortune smile and empty snail-shells abound, she encrusts the whole fabric with them, until it becomes the supreme expression of her artistic taste. Is this so? Or is it not so? Who shall decide?
The nest of Eumenes pomiformis is the size of an average cherry and constructed of pure mortar, without the least outward pebblework. Its shape is exactly similar to that which we have just described. When built upon a horizontal base of sufficient extent, it is a dome with a central neck, funnelled like the mouth of an urn. But when the foundation is reduced to a mere point, as on the twig of a shrub, the nest becomes a spherical capsule, always, of course, surmounted by a neck. It is then a miniature specimen of exotic pottery, a paunchy alcarraza. Its thickens is very slight, less than that of a sheet of paper; it crushes under the least effort of the fingers. The outside is not quite even. It displays wrinkles and seams, due to the different courses of mortar, or else knotty protuberances distributed almost concentrically.
Both Hymenoptera accumulate caterpillars in their coffers, whether domes or jars. Let us give an abstract of the bill of fare. These documents, for all their dryness, possess a value; they will enable whoso cares to interest himself in the Eumenes to perceive to what extent instinct varies the diet, according to the place and season. The food is plentiful, but lacks variety. It consists of tiny caterpillars, by which I mean the grubs of small Butterflies. We learn this from the structure, for we observe in the prey selected by either Hymenopteran the usual caterpillar organism. The body is composed of twelve segments, not including the head. The first three have true legs, the next two are legless, then come two segments with prolegs, two legless segments and, lastly, a terminal segment with prolegs. It is exactly the same structure which we saw in the Ammophila's Grey Worm.
My old notes give the following description of the caterpillars found in the nest of Eumenes Amedei: "a pale green or, less often, a yellowish body, covered with short white hairs; head wider than the front segment, dead-black and also bristling with hairs. Length: 16 to 18 millimetres (.63 to .7 inch.—Translator's Note.); width: about 3 millimetres." (.12 inch.—Translator's Note.) A quarter of a century and more has elapsed since I jotted down this descriptive sketch; and to-day, at Sérignan, I find in the Eumenes' larder the same game which I noticed long ago at Carpentras. Time and distance have not altered the nature of the provisions.