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."