That pretty sparkler of our summer evenings, so often made the
ploughboy's prize, the only brilliant that glitters in the rustic's hat,
the glowworm, (_lampyris noctiluca_,) is not found in such numbers
with us, as in many other places, where these signal tapers glimmer upon
every grassy bank; yet, in some seasons, we have a reasonable sprinkling
of them. Every body probably knows, that the male glowworm is a winged,
erratic animal, yet may not have seen him. He has ever been a scarce
creature to me, meeting perhaps with one or two in a year; and, when
found, always a subject of admiration. Most creatures have their eyes
so placed, as to be enabled to see about them; or, as Hook says of the
house-fly, to be "circumspect animals;" but this male glowworm has a
contrivance, by which any upward or side vision is prevented. Viewed
when at rest, no portion of his eyes is visible, but the head is
margined with a horny band, or plate, being a character of one of the
genera of the order _coleoptera_, under which the eyes are situate.
This prevents all upward vision; and blinds, or winkers, are so fixed
at the sides of his eyes, as greatly to impede the view of all lateral
objects. _See Figures_. The chief end of this creature in his
nightly peregrinations is to seek his mate, always beneath him on the
earth; and hence this apparatus appears designed to facilitate his
search, confining his view entirely to what is before or below him. The
first serves to direct his flight, the other presents the object of his
pursuit: and as we commonly, and with advantage, place our hand over the
brow, to obstruct the rays of light falling from above, which enables us
to see clearer an object on the ground, so must the projecting hood of
this creature converge the visual rays to a point beneath.
Glowworms emit light only for a short period in the year; and I have but
partially observed it after the middle of July. I have collected many of
these pretty creatures on a bank before my house, into which they retire
during the winter, to shine out again when revived by the summer's
warmth; but in this latter season I have frequently missed certain of
my little proteg├ęs, and have reason to apprehend, that they formed the
banquet of a toad, that frequented the same situation.
Observing above, that the glowworm does not emit light after the 14th of
July, I mean thereby that clear, steady light, which has rendered this
creature so remarkable to all persons; for I have repeatedly noticed,
deep in the herbage, a faint evanescent light proceeding from these
creatures, even as late as August and September. This was particularly
manifested September the 28th, 1826. The evening was warm and dewy, and
we observed on the house-bank multitudes of these small evanescent
sparks in the grass. The light displayed was very different from that
which they exhibit in warm summer months. Instead of the permanent green
glow, that illumines all the blades of the surrounding herbage, it was a
pale transient spot, visible for a moment or two, and then so speedily
hidden, that we were obliged, in order to capture the creature, to
employ the light of a candle. The number of them, and their actions,
creeping away from our sight, contrary to that half lifeless dulness
observed in summer, suggested the idea, that the whole body had availed
themselves of this warm, moist evening, to migrate to their winter
station. A single spark or so was to be seen some evenings after this,
but no such large moving parties were discovered again. If we conclude,
that the summer light of the glowworm is displayed as a signal taper,
the appearance of this autumnal light can have no such object in view,
nor can we rationally assign any use of it to the creature itself,
unless, indeed, it serves as a point of union in these supposed
migrations, like the leading call in the flight of night-moving birds.
The activity and numbers of these insects, in the above-mentioned
evening, enabled me to observe the frequent presence and disappearance
of the light of an individual, which did not seem to be the result of
will, but produced by situation. During the time the insect crawled
along the ground, or upon the fine grass, the glow was hidden; but on
its mounting any little blade, or sprig of moss, it turned round and
presented the luminous caudal spot, which, on its falling or regaining
its level, was hidden again.
A summary of the peculiarities of the year 1825, very appropriately
concludes the volume, from which we may be tempted to make future
extracts.