LUMINOUS INSECTS. 417 



him that one of his people, seeing a J ack-d lantern^ pur- 

 sued 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 o^ igncs Jcitiii, 

 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* cannot be thus explained, is obvious. These 

 were probably electrical phenomena: certainly not ex- 

 plosions of phosphuretted hydrogene, as has been sug- 

 gested by some, which must necessarily have been mo- 

 mentary. But that the igiiis fatiius mentioned by Der- 

 ham as having been seen by himself, and which he 

 describes as flitting about a thistle '', was, though he 

 seems of a diff*erent opinion, no other than some lumi- 

 nous 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, 

 ^ Travels, 2d Ed. 334. " Phil. Trans. 1729. 204. 



VOL. II. 2 E 



