the insect was decapitated the rings remained uninterruptedly bright,
but not so brilliant as before: local irritation with a needle always
increased the vividness of the light. The rings in one instance
retained their luminous property nearly twenty-four hours after the
death of the insect. From these facts it would appear probable, that
the animal has only the power of concealing or extinguishing the light
for short intervals, and that at other times the display is
involuntary. On the muddy and wet gravel-walks I found the larvae of
this lampyris in great numbers: they resembled in general form the
female of the English glowworm. These larvae possessed but feeble
luminous powers; very differently from their parents, on the slightest
touch they feigned death and ceased to shine; nor did irritation excite
any fresh display. I kept several of them alive for some time: their
tails are very singular organs, for they act, by a well-fitted
contrivance, as suckers or organs of attachment, and likewise as
reservoirs for saliva, or some such fluid. I repeatedly fed them on
raw meat; and I invariably observed, that every now and then the
extremity of the tail was applied to the mouth, and a drop of fluid
exuded on the meat, which was then in the act of being consumed. The
tail, notwithstanding so much practice, does not seem to be able to
find its way to the mouth; at least the neck was always touched first,
and apparently as a guide.
When we were at Bahia, an elater or beetle (Pyrophorus luminosus,
Illig.) seemed the most common luminous insect. The light in this case
was also rendered more brilliant by irritation. I amused myself one
day by observing the springing powers of this insect, which have not,
as it appears to me, been properly described. [5] The elater, when
placed on its back and preparing to spring, moved its head and thorax
backwards, so that the pectoral spine was drawn out, and rested on the
edge of its sheath. The same backward movement being continued, the
spine, by the full action of the muscles, was bent like a spring; and
the insect at this moment rested on the extremity of its head and
wing-cases. The effort being suddenly relaxed, the head and thorax flew
up, and in consequence, the base of the wing-cases struck the
supporting surface with such force, that the insect by the reaction was
jerked upwards to the height of one or two inches. The projecting
points of the thorax, and the sheath of the spine, served to steady the
whole body during the spring. In the descriptions which I have read,
sufficient stress does not appear to have been laid on the elasticity
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