125 
L A M P Y R I S. 
men, when cut out of the infedh, retained its brilliant ap¬ 
pearance for fome feconds afterwards. 
The glow-worms of this country are only luminous in 
the feafon of procreation, vvliich lads during the fummer 
months; when the females are impregnated, and have de- 
ofited their eggs, they fhine no longer. This circum- 
ance has authorifed the common opinion, that the exhi¬ 
bition of light is made for the purpofe of guiding or in¬ 
viting the male infect. The glow-worms molt frequently af- 
femble in numbers upon dry banks, or under hedges on the 
Tides of unfrequented roads; they are rarely feen on public 
roads or in fields. They do not difplay their light upon 
all nights alike ; fcarcely one of them will be feen for fe- 
veral nights together, and then, as it were by common 
confent, they appear with great fplendour fora few nights, 
after which they again retire. Their dilappearance pro¬ 
bably depends upon their meeting with the male inleft, 
for we have not obferved tliat the ltate of the weather has 
any influence upon them. They commonly begin to 
fhine before it is quite dark, and extinguifh their light 
fome time before the approach of day. It is remarkable 
with what regularity their inftinft guides them in this par¬ 
ticular; we have kept them the whole day in darknels, 
without their fhowing any defire to move or expol'e their 
light; yet in the evening, although purpofely placed near 
burning candles, they crawled about and (hone with bril¬ 
liancy. The light of the glow-worm is always mod vivid 
when the creature is in motion ; it may alfo be excited or 
increafed by turning the infeft on its back, or othervvife 
teazing it. But the luminous appearance is interrupted 
at all times by fliort and irregular periods of either dimi- 
nifhed light or total darknefs ; ufually, however, there are 
two fmali fpots on the lad ring of the abdomen, which 
retain their light whilft the other luminous rings ceafe to 
fhine. 
Of the organs for the production of light, we have the 
following accurate defcription by Mr. Macartney in the 
Phil. Tranf. for 1810. 
“ The light of the glow-worm is known to proceed 
from fome of the lad rings of the abdomen, which, when 
not illuminated, are of a pale yellow colour. Upon the 
internal furface of thefe rings, there is fpread a layer of a 
peculiar foft yellow fubdance, which has been compared 
to pafte; but, by examination with a lens, I found it to be 
organized like the Common interditial fubdance of thein- 
feft’s body, except that it is of a cloler texture, and a pa¬ 
ler yellow colour. This fubdance does not entirely cover 
the inner furface of the rings, being more or lefs deficient 
along their edges, where it prefents an irregular waving 
outline. I have obferved in the glow-worm, that it is 
abforbed, and its place fupplied by common interditial 
fubftance, after the feafon for giving light is pad. The 
fegments of the abdomen, behind which this peculiar fub¬ 
dance is fituated, are thin and tranfparent, in order to ex- 
pofe the internal illumination. The number of luminous 
rings varies in different fpecies of lampyris ; and, as it 
would feem, at different periods in the lame individual. 
“Befides the luminous fubdance above defcribed, I 
have difcovered, in the common glow-worm, on the in¬ 
ner fide of the lad abdominal ring, two bodies, which to 
the naked eye appear more minute than the head of the 
fmalled pin. They are lodged in two flight depreflions, 
formed in the fhell of the ring, which is at thefe points 
particularly tranfparent. On examining thefe bodies un¬ 
der the microfcope, I found that they were facs contain¬ 
ing a foft yellow fubdance, of a more clofe and homoge¬ 
neous texture than that which lines the inner furface" of 
the rings. The membrane forming the facs appeared to 
be of two layers, each of which is compofed of a tranf¬ 
parent filvery fibre, in the fame manner as the internal 
membrane, of the refpiratory tubes of infefts, except that, 
in this cafe, the fibre pafies in a fpiral indead of a circu¬ 
lar direction. This membrane, although l'o delicately 
conftrufted, is fo claftic as to preferve its form after the 
i'-AC is ruptured, and the contents difcharged. The light 
Vol. XII. No. 216. 
that proceeds from thefe facs is lefs under the controul of 
the infett than that of the luminous fubdance fpread oa 
the rings : it is rarely ever entirely extinguilhed in the 
feafon that the glow-worm gives light, even during the 
day; and, when all the other rings are dark, thefe facs of¬ 
ten fhine brightly. As far as my obfervation lias ex¬ 
tended, the fmall facs of luminous fubdances are not found 
in any lpecies of Lampyris except the glow-worm of this 
country. 
“It is worthy of remark, that in all the difTe£tions I 
have made of luminous infefts, I did not find that the 
organs of light were better, or differently fupplied with 
either nerve9 or air-tubes, than the other parts of the 
body. The power of emitting light likewife exids in 
many creatures which want nerves ; a circumdance ftrongly 
marking a difference between animal light and animal 
eleft ricity.” 
The phenomenon of animal light has been attempted 
to be explained in different ways. By many perfons it 
was formerly afcribed to a putrefadfive procefs; but, fince 
the modern theories of combudion became known, it has- 
been generally believed to depend upon an adfual ijflflam- 
mation of the luminous fubdance, limilar to the flow com¬ 
budion of phofphorus. Others have accounted for the 
luminous effetf, by fuppofing the matter of light to be 
accumulated, and rendered latent under particular cir- 
cumltances, and afterwards evolved in a fenfible form. 
The opinion of the light of living animals being the 
confequence of putrefabiion, is evidently abfurd, and con- 
tradiffory to all obfervation on the fubjedt. It has been 
proved by the experiments of Dr. Hulme and others, that 
even the luminous appearances of dead animals are exhi¬ 
bited only during the firft ftages of the dilfolution of the 
body, and that no light is emitted after putrefaction has 
really commenced. Spallanzani, who was the mod dre- 
nuous advocate for the phofphorefcent nature of animal 
light, dated that glow-worms flione more brilliantly when 
put into oxygen gas; that their light gradually difap- 
peared in hydrogen or in azotic gas, and was inftantly 
extinguiflied in fixed air ; that it was alfo loft by cold, 
and revived by the application of a warm temperature. 
He conjedtured that the luminous matter of thefe infedfs 
was compofed of hydrogen and carbonated hydrogen gas. 
Carradori has made fome experiments which led him 
to deny its phofphorefcence. He found that the lumi¬ 
nous portion of the belly of the infect lhone in vacuum, 
in oil, in water, and diderent liquids, and under diderent 
circumdances, where it was excluded from all communi¬ 
cation with oxygen gas. He accounts for the refult of 
Forder’s experiment, by fuppofing, that tire worm flione 
more vividly, becaufe it was more animated in oxygen 
gas than in common air. Ann. di Chimica, 1797. 
The following experiments, which were lately made 
upon this fubjedt by Mr. Macartney, would lead to dif¬ 
ferent conclufions than thole of the preceding authors. 
Experiment 1. A glow-worm was put into a glals of 
water, in which it lived nearly two hours, and continued 
to emit light as ufua), until it died, when the luminous 
appearance entirely ceafed. 
Exp. z. The luminous fubdance rvas extradted from 
the before-mentioned glow-worm, and from others killed 
in different ways ; but it afforded no light. 
Exp. 3. The facs containing the luminous matter were 
cut from the bellies of living glow-worms, and (hone unin¬ 
terruptedly for feveral hours in the atmofphere ; and, af¬ 
ter their light became extindf, it was revived by being 
moidened with water: fome of thefe were put into water 
in the fird indance, in which they continued to fhine un¬ 
remittingly for forty-eight hours. 
Exp. 4. The luminous fubdance of a glow-worm was 
expofed to a degree of beat which would have been fuffi- 
cient to inflame phofphorus, without increafing the bril¬ 
liancy of its light; and farther, it could not be made to 
burn by being applied to a reu-hot iron, or to the flame 
of a candle. 
K k Exp. 
