, or wood, the closed receptacle was evidently an
insuperable obstacle to the warning effluvia.

A layer of cotton-wool two fingers in thickness had the same result. I
placed the female in a large glass jar, and laced a piece of thin cotton
batting over the mouth for a cover; this again guarded the secret of my
laboratory. Not a male appeared.

But when I placed the females in boxes which were imperfectly closed, or
which had chinks in their sides, or even hid them in a drawer or a
cupboard, I found the males arrived in numbers as great as when the
object of their search lay in the cage of open wire-work freely exposed
on a table. I have a vivid memory of one evening when the recluse was
hidden in a hat-box at the bottom of a wall-cupboard. The arrivals went
straight to the closed doors, and beat them with their wings, _toc-toc_,
trying to enter. Wandering pilgrims, come from I know not where, across
fields and meadows, they knew perfectly what was behind the doors of the
cupboard.

So we must abandon the idea that the butterfly has any means of
communication comparable to our wireless telegraphy, as any kind of
screen, whether a good or a bad conductor, completely stops the signals
of the female. To give them free passage and allow them to penetrate to
a distance one condition is indispensable: the enclosure in which the
captive is confined must not be hermetically sealed; there must be a
communication between it and the outer air. This again points to the
probability of an odour, although this is contradicted by my experiment
with the naphthaline.

My cocoons were all hatched, and the problem was still obscure. Should I
begin all over again in the fourth year? I did not do so, for the reason
that it is difficult to observe a nocturnal butterfly if one wishes to
follow it in all its intimate actions. The lover needs no light to
attain his ends; but my imperfect human vision cannot penetrate the
darkness. I should require a candle at least, and a candle would be
constantly extinguished by the revolving swarm. A lantern would obviate
these eclipses, but its doubtful light, interspersed with heavy shadows,
by no means commends it to the scruples of an observer, who must see,
and see well.

Moreover, the light of a lamp diverts the butterflies from their object,
distracts them from their affairs, and seriously compromises the success
of the observer. The moment they enter, they rush frantically at the
flame, singe th