To these observations, long since made, we must add a few very recent ones from Monsieur Macaire, whose ex periments agree in some points with those of former ob servers, and differ in others. These observations were made on the Lampyris noctiluca, and we prefer recording them in as brief a manner as we can, to any attempt to re concile them with former ones; as we know not to whom, among all the naturalists who have investigated this sub ject, credit is most due.
The abdomen in this insect consists of ten segments, the three last of which are of a yellowish colour beneath, the last of all being of the same colour above, while all the rest of the body is brown. On the back there is a re markable ridge, running from the thorax to the end of the tail. The most brilliant light is emitted from the middle of the two antipenultimate segments, and from the sides of the last. The light exhibited by the other parts or the abdomen is feeble, and as if it was obscured by some co vering, except that there is a single luminous point on the fourth segment. A faint light is also displayed by the hin der end of the dorsal line. When the animal is at liberty, the light is consequently downward, but it turns the tail up and agitates, apparently for the purpose of display. At sunrise, the light disappears, with the exception of the two bright points of the last segments ; and it begins first to be visible at seven or eight o'clock in the evening. M. Macaire is further of opinion, that the luminous points .of the last segments are far less under the will of the animal than the other portions.
He objects to the opinion that the light of the glow worm is intended as an attraction to the male, not only be cause the male is itself luminous, but because this pro perty continues throughout the season when there is no in tercourse of this nature. Even at the very moment that the insect quits the egg, when it is a little greenish worm, not more than the twelfth of an inch long, it displays the two luminous points at the end of the tail. As it grows the body becomes black, though no change of shape takes place, and the light continues to increase during the whole of this process.
Our author's remarks on the powers of the animal's will over the light, appear much more particular and accu rate than those of his predecessors. Sometimes noise or agitation cause it to extinguish the light, yet this does not always happen. A sudden blow generally has that effect, but if the insect is, on the contrary, much teased, the light is augmented instead of being diminished. The light of candles or lamps has no effect on it, but that of the sun seems in some way accessory, if not necessary, to the lunrkinous effect, as in the cases of the minerals which phosphoresce from exposure to it. When the insects
were inclosed in a box, they seldom showed their light when this was opened at night, particularly on the first day. But by covering one side of it with a glass, and treating in the same manner, they always yielded a brilliant light at night. When the light is about to be ex tinguished voluntarily, it first disappears from the fore most segments and proceeds backwards ; though the two luminous points on the last often continue to shine after the rest has ceased. M. Macaire attempted in vain to discover by what means this observation was produced. He that no membrane is drawn over it ; but having traced some flesh-coloured filaments into the lu minous organ, he considers that the cause consists in some species of nervous action. No effect on the strength of the light was produced, as far as his observations went, by deprivation of food, or by thundery or stormy weather.
The Lampyris Italica is far more brilliant than these, and is the common fire-fly of Italy. The ladies in that country, according to Sir James Smith, stick these in sects into their hair at night as ornaments ; and a similar practice with regard to some other luminous insects, is followed by females in India. It is probable that all the species of this genius have the same property, but it has not been absolutely ascertained.
In the genus Elater, the Noctilucus is the common fire fly of the West Indies. This insect is about an inch long, and one-third of an inch broad, and it gives out its principal light from two transparent tubercles on the thorax ; there are also two luminous patches under the elytra, which are not visible except when the insect is flying, when it appears adorned with four brilliant gems of a most resplendent colour, besides which the whole body is so luminous that the light shines out between the abdominal segments when they are separated by stretching the body. The light is so considerable that the smallest print may be read by it ; and it is said that in former times the inhabitants of St. Domingo not only used them as lights for domestic pur poses, but used to tie them on their persons in travelling, in hunting, and in fishing. They are also used as decora tions on holidays ; the young men fastening them to their persons and horses, and thus galloping about the streets so as to present a moving blaze of light. The ladies are also adorned with them as gems. In the same genus, the ignitus and many others are known to be luminous ; but it is not certain if all the species, which amount to twelve, have this property.