While the twig was sliding away with its band of investigators two new arrivals appeared.  The chair lay in their path.  They stopped at it and searched eagerly at the very spot on which the twig had been lying.  But with these, as with the others, the real object of their desires was there, close by, under a wire cover which was not even veiled.  None took any note of it.  On the floor, a handful of butterflies were still hustling the bunch of leaves on which the female had reposed that morning; others, on the chair, were still examining the spot where the twig had lain.  The sun sank, and the hour of departure struck.  Moreover, the emanations were growing feebler, were evaporating.  Without more ado the visitors left.  We bade them goodbye till the morrow.

The following tests showed me that the leaf-covered twig which accidentally enlightened me might be replaced by any other substance.  Some time before the visitors were expected I placed the female on a bed of cloth or flannel, card or paper.  I even subjected her to the rigours of a camp-bed of wood, glass, marble, and metal.  All these objects, after a contact of sufficient duration, had the same attraction for the males as the female moth herself.  They retained this property for a longer or shorter time, according to their nature.  Cardboard, flannel, dust, sand, and porous objects retained it longest.  Metals, marble, and glass, on the contrary, quickly lost their efficacy.  Finally, anything on which the female had rested communicated its virtues by contact; witness the butterflies crowding on the straw-bottomed chair after the twig fell to the ground.

Using one of the most favourable materials—­flannel, for example—­I witnessed a curious sight.  I placed a morsel of flannel on which the mother moth had been lying all the morning at the bottom of a long test-tube or narrow-necked bottle, just permitting of the passage of a male moth.  The visitors entered the vessels, struggled, and did not know how to extricate themselves.  I had devised a trap by means of which I could exterminate the tribe.  Delivering the prisoners, and removing the flannel, which I placed in a perfectly closed box, I found that they re-entered the trap; attracted by the effluvia that the flannel had communicated to the glass.

I was now convinced.  To call the moths of the countryside to the wedding-feast, to warn them at a distance and to guide them the nubile female emits an odour of extreme subtlety, imperceptible to our own olfactory sense-organs.  Even with their noses touching the moth, none of my household has been able to perceive the faintest odour; not even the youngest, whose sensibility is as yet unvitiated.

This scent readily impregnates any object on which the female rests for any length of time, when this object becomes a centre of attraction as active as the moth herself until the effluvium is evaporated.

Nothing visible betrays the lure.  On a sheet of paper, a recent resting-place, around which the visitors had crowded, there was no visible trace, no moisture; the surface was as clean as before the impregnation.