M. Lacordaire,—an authority on South American insects second to none, says that he himself indeed never saw a luminous Fulgora all the time he was collecting in Brazil and Cayenne, and that most of the inhabitants of the latter country, when questioned on the subject, denied the fact, yet that others of the natives as distinctly affirmed that it is luminous. He asks whether it is not possible that the light may be confined to one sex, and thus the conflicting testimony be reconciled; and gives it as his opinion that the point is rather one which requires more careful observation, than one which we can consider absolutely decided.[150]
Again, the Marquis Spinola, in an elaborate paper on this tribe, published in the Annals of the Entomological Society of France,[151] strenuously contends that the remarkable development of the frontal portion of the head in the whole race is luminous. And finally, a friend of Mr Wesmael assured him that he had himself seen the American Fulgora luminous while alive.[152]
It may help to sustain our faith in the veracity of Madame Merian, to know that there is some reason for attributing occasional luminosity to well-known English insects, of which hundreds, and even thousands, have been taken without manifesting a trace of the phenomenon. Mr Spence, in his interesting Letter on Luminous Insects,[153] adduces the following evidence:—Insects "may be luminous which have not hitherto been suspected of being so. This seems proved by the following fact: A learned friend 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 shewn 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 shew 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 globes seen by Dr Shaw cannot be thus explained, is obvious. These were probably electrical phenomena; certainly not explosions of phosphuretted hydrogen, 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, 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 motion 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 anything of the kind; and from the silence of other philosophers of our own times, it should seem that their experience is similar."
A paper by Mr R Chambers on the subject adduces the additional testimony of facts observed by good naturalists, as Dickson and Curtis the eminent botanists, and Stothard the painter and entomologist, by his own father Mr A. Chambers, and by Joseph Simpson, a fisherman living near Boston, all of which strongly corroborate the probability that some, at least, of the ignes fatui are produced by luminous insects.[154] Mr Main narrates the case of a farmer who stated that he had pursued a Will-o'-the-wisp, and coming up with it had knocked it down, when it proved to be an insect "exactly like a Maggy-long-legs"—that is, the common Crane-fly (Tipula oleracea), the very insect with which Mr Sheppard had compared the motions of the luminous flame observed by him.[155] Mr Spence argues that while gaseous emanations may be a cause of stationary ignes fatui, the same cause will not explain those which flit along from place to place; and that these are probably luminous insects, however rarely they may have come under the notice of entomologists. "A very strong argument for the possibility of some flying insects being occasionally luminous (in England) is afforded by the facts ... of luminous caterpillars having been within these few years observed for the first time since entomology has been attended to, and that by observers every way competent. If caterpillars so very common as those of Mamestra oleracea may sometimes, though so rarely, be luminous, and if, as Dr Boisduval suggests, and is very probable, this appearance was caused by disease, it is obvious that flying insects may be also occasionally (though seldom) luminous from disease—a supposition which will at once explain the rarity of the occurrence, and the circumstance that insects of such different genera, and even orders, are said to have exhibited this phenomenon."[156]
These highly curious facts should make observers cautious in strongly denying statements made by others of phenomena, when they themselves have not been so fortunate as to witness them, even though they may think their opportunities to have been as favourable as those of the soi-disant observer.[157]
But we have not yet dismissed Madame Merian. If acquitted of falsehood here, she stands arraigned on a second charge of similar character.
In most tropical countries there are found hideous hairy spiders of monstrous size and most repulsive appearance; short-legged, sombre-hued, ferocious marauders of the night, that by day lurk in obscure retreats under stones, or in burrows in the earth.
Guiana produces a formidable species of this sort (Mygale avicularia), which measures three inches in length, and whose feet—though the genus is, as I have said, comparatively short-limbed—cover an area some eight or ten inches in diameter. Madame Merian has exquisitely figured the tragical end of a tiny humming-bird, surprised by one of these monsters on her eggs; the petite bird overthrown under the fangs of the sprawling spider, one of whose feet is in the nest. It was on the authority of this lady that Linnæus gave the name of avicularia to the species. Later naturalists have scouted the whole story. Mr MacLeay, who resided in Cuba, says that there are indeed there huge spiders, allied to our garden spider, which make a geometric net, strong enough to embarrass small birds; but that these do not attempt to catch such prey, and never molest birds at all. On the other hand, he avers that the Cuban Mygale, an allied species to that of Guiana, makes no web, and has no power of injuring birds. He put this to the test of experiment; for having maimed a humming-bird, he thrust it into the Mygale's hole, which, instead of seizing the victim, retreated as in fear out of his den. This Mr MacLeay supposes to be conclusive; but a moment's reflection will shew how equivocal is the evidence. The spider may not have been hungry; or he may have been taken aback by the sudden intrusion; or he might not choose to take prey that he had not stolen upon and slaughtered suo more; or he may have muttered in the Arachnidan language,—
"Timeo Danaos, et dona ferentes."