a free control of the light which he emits? Can he turn it on or down
or put it out as he pleases? Has he an opaque screen which is drawn
over the flame at will, or is that flame always left exposed? There is
no need for any such mechanism: the insect has something better for
its revolving light.

The thick tube supplying the light-producing sheet increases the flow
of air and the light is intensified; the same air-tube, swayed by the
animal's will, slackens or even suspends the passage of air and the
light grows fainter or even goes out. It is, in short, the mechanism
of a lamp which is regulated by the access of air to the wick.

Excitement can set the attendant air-duct in motion. We must here
distinguish between two cases: that of the gorgeous scarves, the
exclusive ornament of the female ripe for matrimony, and that of the
modest fairy-lamp on the last segment, which both sexes kindle at any
age. In the second case, the extinction caused by a flurry is sudden
and complete, or nearly so. In my nocturnal hunts for young
Glow-worms, measuring about 5 millimetres long,[3] I can plainly see
the glimmer on the blades of grass; but, should the least false step
disturb a neighbouring twig, the light goes out at once and the
coveted insect becomes invisible. Upon the full-grown females, lit up
with their nuptial scarves, even a violent start has but a slight
effect and often none at all.

[Footnote 3: .195 inch.--_Translator's Note_.]

I fire a gun beside a wire-gauze cage in which I am rearing my
menagerie of females in the open air. The explosion produces no
result. The illumination continues, as bright and placid as before. I
take a spray and rain down a slight shower of cold water upon the
flock. Not one of my animals puts out its light; at the very most,
there is a brief pause in the radiance; and then only in some cases. I
send a puff of smoke from my pipe into the cage. This time, the pause
is more marked. There are even some extinctions, but these do not last
long. Calm soon returns and the light is renewed as brightly as ever.
I take some of the captives in my fingers, turn and return them, tease
them a little. The illumination continues and is not much diminished,
if I do not press too hard with my thumb. At this period, with the
pairing close at hand, the insect is in all the fervour of its
passionate splendour; and nothing short of very serious reasons would
make it put out its signals altogether.

All thi