Three years went by and by chance two more cocoons of the Monk or Oak Eggar again fell into my hands.  Both produced females, at an interval of a few days towards the middle of August; so that I was able to vary and repeat my experiments.

I rapidly repeated the experiments which had given me such positive results in the instance of the Great Peacock moth.  The pilgrims of the day were no less skilful at finding their mates than the pilgrims of the night.  They laughed at all my tricks.  Infallibly they found the prisoners in their wire-gauze prisons, no matter in what part of the house they were placed; they discovered them in the depths of a wall-cupboard; they divined the secret of all manner of boxes, provided these were not rigorously air-tight.  They came no longer when the box was hermetically sealed.  So far this was only a repetition of the feats of the Great Peacock.

A box perfectly closed, so that the air contained therein had no communication with the external atmosphere, left the male in complete ignorance of the recluse.  Not a single one arrived, even when the box was exposed and plain to see on the window-sill.  Thus the idea of strongly scented effluvia, which are cut off by screens of wood, metal, card, glass, or what not, returns with double force.

I have shown that the great nocturnal moth was not thrown off the scent by the powerful odour of naphthaline, which I thought would mask the extra-subtle emanations of the female, which were imperceptible to human olfactory organs.  I repeated the experiment with the Oak Eggar.  This time I used all the resources of scent and stench that my knowledge of drugs would permit.

A dozen saucers were arranged, some in the interior of the wire-gauze cover, the prison of the female, and some around it, in an unbroken circle.  Some contained naphthaline; others the essential oil of spike-lavender; others petroleum, and others a solution of alkaline sulphur giving off a stench of rotten eggs.  Short of asphyxiating the prisoner I could do no more.  These arrangements were made in the morning, so that the room should be saturated when the congregation of lovers should arrive.

In the afternoon the laboratory was filled with the most abominable stench, in which the penetrating aroma of spike-lavender and the stink of sulphuretted hydrogen were predominant.  I must add that tobacco was habitually smoked in this room, and in abundance.  The concerted odours of a gas-works, a smoking-room, a perfumery, a petroleum well, and a chemical factory—­would they succeed in confusing the male moths?

By no means.  About three o’clock the moths arrived in as great numbers as usual.  They went straight to the cage, which I had covered with a thick cloth in order to add to their difficulties.  Seeing nothing when once they had entered, and immersed in an extraordinary atmosphere in which any subtle fragrance should have been annihilated, they nevertheless made straight for the prisoner, and attempted to reach her by burrowing under the linen cloth.  My artifice had no result.