Spanish West India islands not only instead of candles, but as
extirpators of the gnats, which are a dreadful pest to the inhabitants
of the low grounds. They introduce a few fire-flies, to which the
gnats are a grateful food, into their houses, and by means of these
"commodious hunters" are soon rid of the intruders. "How they are a
remedy," says this author, "for so great a mischiefe it is a pleasant
thing to hear. Hee who understandeth he hath those troublesome guestes
(the gnattes) at home, diligently hunteth after the Cucuij. Whoso
wanteth Cucuij goeth out of the house in the first twilight of the
night, carrying a burning fire-brande in his hande, and ascendeth
the next hillock that the Cucuij may see it, and hee swingeth the
fire-brande about, calling Cucuius aloud, and beating the ayre with
often calling out _Cucuie, Cucuie_." He goes on to observe, that the
simple people believe the insect is attracted by their invitations;
but that, for his part he is rather inclined to think that the fire
is the magnet. Having obtained a sufficient number of Cucuij, the
beetle-hunter returns home and lets them fly loose in the house, where
they diligently seek the gnats about the beds and the faces of those
asleep, and devour them[693].--These insects are also applied to
purposes of decoration. On certain festival days in the month of June,
they are collected in great numbers, and tied all over the garments of
the young people, who gallop through the streets on horses similarly
ornamented, producing on a dark evening the effect of a large moving
body of light. On such occasions the lover displays his gallantry by
decking his mistress with these living gems[694]. And according to P.
Martire, "many wanton wilde fellowes" rub their faces with the flesh of
a killed Cucuius, as boys with us use phosphorus, "with purpose to meet
their neighbours with a flaming countenance," and derive amusement from
their fright.
Besides _Elater noctilucus_, _E. ignitus_ and several others of
the same genus are luminous. Not fewer than twelve species of this
family are described by Illiger in the _Berlin Naturalist Society's
Magazine_[695].
The brilliant nocturnal spectacle presented by these insects to the
inhabitants of the countries where they abound cannot be better
described than in the language of the poet above referred to, who has
thus related its first effect upon the British visitors of the new
world:
"..............Sorrowing we beheld
The night come on; but soon did night display
More wonders than it veil'd: innumerous tribes
From the wood-cover swarm'd, and darkness made
Their beauties visible: one while they stream'd
A bright blue radiance upon flowers that closed
Their gorgeous colours from the eye of day;
Now motionless and dark, eluded search,
Self-shrouded; and anon, starring the sky,
Rose like a shower of fire."
The beautiful poetical imagery with which Mr. Southey has decorated
this and a few other entomological facts, will make you join in my
regret that a more extensive acquaintance with the science has not
enabled him to spread his embellishments over a greater number.
The gratification which the entomologist derives from seeing his
favourite study adorned with the graces of poetry is seldom unalloyed
with pain, arising from the inaccurate knowledge of the subject
in the poet. Dr. Darwin's description of the beetle to which the
nut-maggot is transformed may delight him (at least if he be an
admirer of the Darwinian style) as he reads for the first time,
"So sleeps in silence the Curculio, shut
In the dark chamber of the cavern'd nut;
Erodes with ivory beak the vaulted shell,
And quits on filmy wings its narrow cell."
But when the music of the lines has allowed him room for pause,
and he recollects that they are built wholly upon an incorrect
supposition, the Curculio never inhabiting the nut in its beetle
shape, nor employing its ivory or rather ebony beak upon it, but
undergoing its transformation under ground, he feels disappointed
that the passage has not truth as well as sound.--Mr. Southey, too,
has fallen into an error: he confounds the fire-fly of St. Domingo
(_Elater noctilucus_) with a quite different insect, the lantern-fly
(_Fulgora laternaria_) of Madame Merian; but happily this error does
not affect his poetry.
But to return from this digression.--If we are to believe Mouffet,
(and the story is not incredible,) the appearance of the tropical
fire-flies on one occasion led to a more important result than might
have been expected from such a cause. He tells us, that when Sir
Thomas Cavendish and Sir Robert Dudley first landed in the West
Indies, and saw in the evening an infinite number of moving lights in
the woods, which were merely these insects, they supposed that the
Spaniards were advancing upon them, and immediately betook themselves
to their ships[696]:--a result as well entitling the Elaters to
a commemoration feast, as a similar good office the land-crabs
of Hispaniola, which, as the Spaniards tell, (and the story is
confirmed by an anniversary _Fiesta de lôs Cangrejos_,) by their
clattering--mistaken by the enemy for the sound of Spanish cavalry
close upon their heels--in like manner scared away a body of English
invaders of the city of St. Domingo[697].
An anecdote less improbable, perhaps, and certainly more ludicrous,
is related by Sir J. E. Smith of the effect of the first sight of
the Italian glow-worms upon some Moorish ladies ignorant of such
appearances. These females had been taken prisoners at sea, and,
until they could be ransomed, lived in a house in the outskirts
of Genoa, where they were frequently visited by the respectable
inhabitants of the city; a party of whom, on going one evening,
were surprised to find the house closely shut up, and their Moorish
friends in the greatest grief and consternation. On inquiring into
the cause, they ascertained that some of the _Pygolampis italica_
had found their way into the dwelling, and that the ladies within
had taken it into their heads that these brilliant guests were no
other than the troubled spirits of their relations; of which idea it
was some time before they could be divested.--The common people in
Italy have a superstition respecting these insects somewhat similar,
believing that they are of a spiritual nature, and proceed out of the
graves, and hence carefully avoid them[698].
The insects hitherto adverted to have been beetles, or of the order
_Coleoptera_. But besides these, a genus in the order _Hemiptera_,
called _Fulgora_, includes several species which emit so powerful
a light as to have obtained in English the generic appellation of
_Lantern-flies_. Two of the most conspicuous of this tribe are the
_F. laternaria_ and _F. candelaria_; the former a native of South
America, the latter of China. Both, as indeed is the case with the
whole genus, have the material which diffuses their light included in
a hollow subtransparent projection of the head. In _F. candelaria_
this projection is of a subcylindrical shape, recurved at the apex,
above an inch in length, and the thickness of a small quill. We may
easily conceive, as travellers assure us, that a tree studded with
multitudes of these living sparks, some at rest and others in motion,
must at night have a superlatively splendid appearance.--In _F.
laternaria_, which is an insect two or three inches long, the snout
is much larger and broader, and more of an oval shape, and sheds a
light the brilliancy of which transcends that of any other luminous
insect. Madame Merian informs us, that the first discovery which
she made of this property caused her no small alarm. The Indians had
brought her several of these insects, which by day-light exhibited no
extraordinary appearance, and she inclosed them in a box until she
should have an opportunity of drawing them, placing it upon a table
in her lodging-room. In the middle of the night the confined insects
made such a noise as to awake her, and she opened the box, the inside
of which to her great astonishment appeared all in a blaze; and in
her fright letting it fall, she was not less surprised to see each
of the insects apparently on fire. She soon, however, divined the
cause of this unexpected phenomenon, and re-inclosed her brilliant
guests in their place of confinement. She adds, that the light of
one of these _Fulgoræ_ is sufficiently bright to read a newspaper
by: and though the tale of her having drawn one of these insects by
its own light is without foundation, she doubtless might have done
so if she had chosen[699].--Another species (_F. pyrrhorynchus_) is
figured by Mr. Donovan in his _Insects of India_, of which the light,
though from a smaller snout than that of _F. laternaria_, must assume
a more splendid and striking appearance, the projection being of a
rich deep purple from the base to near the apex, which is of a fine
transparent scarlet; and these tints will of course be imparted to
the transmitted light.
In addition to the insects already mentioned, some others have the
power of diffusing light, as two species of _Centipedes_ (_Geophilus
electricus_ and _phosphoreus_), and probably others of the same genus.
In these the light is not confined to one part, but proceeds from
the whole body. _G. electricus_ is a common insect in this country,
residing under clods of earth, and often visible at night in gardens.
_G_? _phosphoreus_, a native of Asia, is an obscure species, described
by Linné, on the authority of C. G. Ekeberg, the captain of a Swedish
East Indiaman, who asserted that it dropped from the air, shining like
a glow-worm, upon his ship, when sailing in the Indian ocean a hundred
miles (Swedish) from the continent. However singular this statement,
it is not incredible. The insect may either, as Linné suspects, have
been elevated into the atmosphere by wings with which, according to
him, one species of the genus is provided; or more probably, perhaps,
by a strong wind, such as that which raised into the air the shower of
insects mentioned by De Geer as occurring in Sweden in the winter of
1749, after a violent storm that had torn up trees by the roots, and
carried away to a great distance the surrounding earth, and insects
which had taken up their winter quarters amongst it[700]. That the
wind may convey the light body of an insect to the above-mentioned
distance from land, you will not dispute when you call to mind that our
friend Hooker, in his interesting _Tour in Iceland_, tells us that the
ashes from the eruption of one of the Icelandic volcanos in 1755 were
conveyed to Ferrol, a distance of upwards of 300 miles[701].--Lastly,
to conclude my list of luminous insects, Professor Afzelius observed "a
dim phosphoric light" to be emitted from the singular hollow antennæ
of _Pausus sphærocerus_[702]. A similar appearance has been noticed
in the eyes of _Acronycta Psi_, _Cossus ligniperda_, and other moths.
_Chiroscelis bifenestrata_ of Lamarck, a beetle, has two red oval spots
covered with a downy membrane on the second segment of the abdomen,
which he thinks indicate some particular organ perhaps luminous[703]:
and M. Latreille informs me that a friend of his, who saw one living
which was brought from China to the Isle of France in wood, found that
the _ocelli_ in the elytra of _Buprestis ocellata_ were luminous.
But besides the insects here enumerated, others may be luminous which
have not hitherto been suspected of being so. This seems proved by the
following fact. A learned friend[704] has informed me, that when he was
curate of Ickleton, Cambridgeshire, in 1780, a farmer of that place of
the name of Simpringham brought to him a mole-cricket (_Gryllotalpa
vulgaris_, Latr.), and told him that one of his people, seeing a
_Jack-o'lantern_, pursued it and knocked it down, when it proved to be
this insect, and the identical specimen shown to him.
This singular fact, while it renders it probable that some insects
are luminous which no one has imagined to be so, seems to afford
a clue to the, at least, partial explanation of the very obscure
subject of _ignes fatui_, and to show that there is considerable
ground for the opinion long ago maintained by Ray and Willughby,
that the majority of these supposed meteors are no other than
luminous insects. That the large varying lambent flames, mentioned by
Beccaria to be very common in some parts of Italy, and the luminous
globe seen by Dr. Shaw[705] cannot be thus explained, is obvious.
These were probably electrical phenomena: certainly not explosions
of phosphuretted hydrogene, as has been suggested by some, which
must necessarily have been momentary. But that the _ignis fatuus_
mentioned by Derham as having been seen by himself, and which he
describes as flitting about a thistle[706], was, though he seems of a
different opinion, no other than some luminous insect, I have little
doubt. Mr. Sheppard informs me that, travelling one night between
Stamford and Grantham on the top of the stage, he observed for more
than ten minutes a very large _ignis fatuus_ in the low marshy
grounds, which had every appearance of being an insect. The wind was
very high: consequently, had it been a vapour, it must have been
carried forward in a direct line; but this was not the case. It had
the same motions as a Tipula, flying upwards and downwards, backwards
and forwards, sometimes appearing as settled, and sometimes as
hovering in the air.--Whatever be the true nature of these meteors,
of which so much is said and so little known, it is singular how few
modern instances of their having been observed are on record. Dr.
Darwin declares, that though in the course of a long life he had been
out in the night, and in the places where they are said to appear,
times without number, he had never seen any thing of the kind: and
from the silence of other philosophers of our own times, it should
seem that their experience is similar.
* * * * *
With regard to the immediate source of the luminous properties of
these insects, Mr. Macartney, to whom we are indebted for the most
recent investigation on the subject, has ascertained that in the
common glow-worm, and in _Elater noctilucus_ and _ignitus_, the light
proceeds from masses of a substance not generally differing, except in
its yellow colour, from the interstitial substance (_corps graisseux_)
of the rest of the body, closely applied underneath those transparent
parts of the insects' skin which afford the light. In the glow-worm,
besides the last-mentioned substance, which, when the season for giving
light is passed, is absorbed, and replaced by the common interstitial
substance, he observed on the inner side of the last abdominal segment
two minute oval sacs formed of an elastic spirally-wound fibre similar
to that of the tracheæ, containing a soft yellow substance of a closer
texture than that which lines the adjoining region, and affording a
more permanent and brilliant light. This light he found to be less
under the control of the insect than that from the adjoining luminous
substance, which it has the power of voluntarily extinguishing, not
by retracting it under a membrane, as Carradori imagined, but by
some inscrutable change dependent upon its will: and when the latter
substance was extracted from living glow-worms it afforded no light,
while the two sacs in like circumstances shone uninterruptedly for
several hours. Mr. Macartney conceives, from the radiated structure
of the interstitial substance surrounding the oval yellow masses
immediately under the transparent spots in the thorax of _Elater
noctilucus_, and the subtransparency of the adjoining crust, that the
interstitial substance in this situation has also the property of
shining--a supposition which, if De Geer and other authors be correct
in stating that this insect has two luminous patches under its elytra,
and that the incisures between the abdominal segments shine when
stretched, may probably be extended to the _whole_ of the interstitial
substance of its body.--What peculiar organization contributes to the
production of light in the hollow projections of _Fulgora laternaria_
and _candelaria_, the hollow antennæ of _Pausus sphærocerus_, and
under the whole integument of _Geophilus electricus_, Mr. Macartney
was unable to ascertain. Respecting this last he remarks, what I have
myself observed, that there is an apparent effusion of a luminous fluid
on its surface, that may be received upon the hand, which exhibits a
phosphoric light for a few seconds afterwards; and that it will not
shine unless it have been previously exposed for a short time to the
solar light[707].
With respect to the remote cause of the luminous property of insects,
philosophers are considerably divided in opinion. The disciples
of modern Chemistry have in general, with Dr. Darwin, referred it
to the slow combustion of some combination of phosphorus secreted
from their fluids by an appropriate organization, and entering into
combination with the oxygene supplied in respiration. This opinion
is very plausibly built upon the ascertained existence of phosphoric
acid as an animal secretion; the great resemblance between the light
of phosphorus in slow combustion and animal light; the remarkably
large spiracula in glow-worms; and upon the statement, that the light
of the glow-worm is rendered more brilliant by the application of
heat and oxygene gas, and is extinguished by cold and by hydrogene
and carbonic acid gases. From these last facts Spallanzani was led to
regard the luminous matter as a compound of hydrogene and carburetted
hydrogene gas. Carradori having found that the luminous portion of
the belly of the Italian glow-worm (_Pygolampis italica_) shone in
vacuo, in oil, in water, and when under other circumstances where
the presence of oxygene gas was precluded, with Brugnatelli ascribed
the property in question to the imbibition of light separated from
the food or air taken into the body, and afterwards secreted in
a sensible form[708]. Lastly, Mr. Macartney having ascertained
by experiment that the light of a glow-worm is not diminished by
immersion in water, or increased by the application of heat; that the
substance affording it, though poetically employed for lighting the
fairies' tapers[709], is incapable of inflammation if applied to
the flame of a candle or red-hot iron; and when separated from the
body exhibits no sensible heat on the thermometer's being applied to
it--rejects the preceding hypotheses as unsatisfactory, but without
substituting any other explanation; suggesting, however, that the
facts he observed are more favourable to the supposition of light
being a quality of matter than a substance[710].
Which of these opinions is the more correct I do not pretend to
decide. But though the experiments of Mr. Macartney seem fairly to
bear him out in denying the existence of any ordinary combination of
phosphorus in luminous insects, there exists a contradiction in many
of the statements, which requires reconciling before final decision
can be pronounced. The different results obtained by Forster and
Spallanzani, who assert that glow-worms shine more brilliantly in
oxygene gas, and by Beckerheim, Dr. Hulme, and Sir H. Davy, who
could perceive no such effect, may perhaps be accounted for by the
supposition that in the latter instances the insects having been
taken more recently, might be less sensible to the stimulus of the
gas than in the former, where possibly their irritability was, as
Brown would say, accumulated by a longer abstinence: but it is not
so easy to reconcile the experiment of Sir H. Davy, who found the
light of the glow-worm not to be sensibly diminished in hydrogene
gas[711], with those of Spallanzani and Dr. Hulme, who found it
to be extinguished by the same gas, as well as by carbonic acid,
nitrous and sulphuretted hydrogene gases[712]. Possibly some of
these contradictory results were occasioned by not adverting to the
faculty which the living insect possesses of extinguishing its lights
at pleasure; or different philosophers may have experimented on
different species of Lampyris.
The general use of this singular provision is not much more
satisfactorily ascertained than its nature. I have before
conjectured--and in an instance I then related it seemed to be so--that
it may be a means of defence against their enemies[713]. In different
kinds of insects, however, it may probably have a different object.
Thus in the lantern-flies (_Fulgora_), whose light precedes them, it
may act the part that their name imports, enabling them to discover
their prey, and to steer themselves safely in the night. In the
fire-flies (_Elater_), if we consider the infinite numbers that in
certain climates and situations present themselves every where in the
night, it may distract the attention of their enemies or alarm them.
And in the glow-worm--since their light is usually most brilliant in
the female; in some species, if not all, present only in the season
when the sexes are destined to meet; and strikingly more vivid at the
very moment when the meeting takes place[714]--besides the above uses,
it is most probably intended to conduct the sexes to each other. This
seems evidently the design in view in those species in which, as in the
common glow-worm (_L. noctiluca_), the females are apterous. The torch
which the wingless female, doomed to crawl upon the grass, lights up at
the approach of night, is a beacon which unerringly guides the vagrant
male to her "love-illumined form," however obscure the place of her
abode. It has been objected, however, to this explanation, that--since
both larva and pupa, as De Geer observed[715], and the males shine
as well as the females--the meeting of the sexes can scarcely be the
object of their luminous provision. But this difficulty appears to me
easily surmounted. As the light proceeds from a peculiarly organized
substance, which probably must in part be elaborated in the larva and
pupa states, there seems nothing inconsistent in the fact of _some_
light being then emitted with the supposition of its being destined
solely for use in the perfect state: and the circumstance of the male
having the same luminous property, no more proves that the superior
brilliancy of the female is not intended for conducting him to her,
than the existence of nipples and sometimes of milk in man proves that
the breast of woman is not meant for the support of her offspring. We
often see without being able to account for the fact, except on Sir E.
Home's idea, that the sex of the ovum is undetermined[716], traces of
an organization in one sex indisputably intended for the sole use of
the other.
I am, &c.
FOOTNOTES:
[685] _Hist. Ins._ 81.
[686] _Hist. abreg._ i. 168.
[687] Illiger _Mag._ iv. 195.
[688] _Nat. Hist._ ii. 279.
[689] Geoffr. i. 167. De Geer, iv. 35.
[690] I call by this name all those _Lampyridæ_ whose head is not at
all, or but little, concealed by the shield of the prothorax, and
both sexes of which are winged.
[691] VOL. I. 317.
[692] Pietro Martire, _The Decades of the New World_, quoted in
_Madoc_, p. 543.
[693] P. Martire, _ubi supr._
[694] Walton's _Present State of the Spanish Colonies_, i. 128.
[695] _Iahrgang_, i. 141.
[696] 112.
[697] Walton's _Hispaniola_, i. 39.
[698] _Tour on the Continent_, 2d Edit. iii. 85.
[699] _Ins. Sur._ 49.--The above account of the luminous properties
of _Fulgora laternaria_ is given, because negative evidence ought not
hastily to be allowed to set aside facts positively asserted by an
author whose veracity is unimpeached; but it is necessary to state,
that not only have several of the inhabitants of Cayenne, according
to the French _Dictionnaire d'Histoire Naturelle_, denied that this
insect shines, in which denial they are joined by M. Richard, who
reared the species (_Encyclopédie_, art. _Fulgora_); but the learned
and accurate Count Hoffmansegg informs us, that his insect collector
Sieber, a practised entomologist of thirty years standing, and who,
when in the Brazils for some years, took many specimens, affirms that
he never saw a single one in the least luminous. _Der Gesellschaft
Naturf. Fr. zu Berlin Mag._ i. 153.
[700] De Geer, iv. 63.--These insects, which were chiefly
_Brachyptera_ L., _Aphodii_, spiders, caterpillars, but particularly
the larvæ of _Telephorus fuscus_, fell in such abundance that they
might have been taken from the snow by handfuls.--Other showers of
insects which have been recorded, as that in Hungary, 20th November
1672 (_Ephem. Nat. Curios._ 1673. 80.), and one mentioned in the
newspapers of July 2d, 1810, to have fallen in France the January
preceding, accompanied by a shower of red snow, may evidently be
explained in the same manner.
[701] p. 407.
[702] _Linn. Trans._ iv. 261.
[703] Latr. _Hist. Nat._ x. 262.
[704] Rev. Dr. Sutton of Norwich.
[705] _Travels_, 2d Ed. 334.
[706] _Phil. Trans._ 1729. 204.
[707] _Phil. Trans._ 1810, p. 281.--Mr. Macartney's statement on this
point is not very clear. He probably means that the insect will not
shine in a dark place in the _day time_, unless previously exposed to
the solar light: for it is often seen to shine at night when it could
have had no _recent_ exposure to the sun.
[708] _Annal. di Chimica_, xiii. 1797. _Phil. Mag._ ii. 80.
[709]
"And for night-tapers crop their waxen thighs,
And light them at the fiery glow-worms' eyes."