PAIRING OF INSECTS. 227 



the appearance of this autumnal light can have no 

 such object in view, nor can we rationally assign any 

 use of it to the creature itself, unless, indeed, it serves 

 as a point of union in these supposed migrations, 

 like the leading call in the flight of night-moving 

 birds*" 



We suspect, however, that these ingenious con- 

 jectures are altogether founded on mistake. It is 

 not correct to say with our author, that the glow- 

 worms "retire during the winter to shine out again 

 when revived by the summer's warmth t ; "for, as we 

 have seen above, both the males and females uni- 

 formly die a few days after pairing ; and we have nd 

 doubt that those which he observed at the end of 

 September were the grubs hatched in the preceding 

 summer, and which differ little in appearance from 

 the perfect female. We found several such grubs 

 in September, at Havre de Grace. Mr. Knapp's 

 mention of birds reminds us of other conjectures re- 

 specting the design of the glow-worm's light, which, 

 according to Kirby and Spence, " may defend them 

 from the attack of some enemies," in the same way 

 as they think the golden wasps (Chrysididcr, LEACH) 

 " are adorned with the most brilliant colours, which 

 by their radiance, especially in the sunny situations 

 frequented by those insects, may dazzle the eyes of 

 their enemies, and enable them to effect unhurt the 

 purpose for which they were created J." But in a 

 subsequent page they remark, that " female glow- 

 worms have the faculty of extinguishing or concealing 

 their light, a very necessary provision to guard them 

 from the attacks of the nightingale, and other noc- 

 turnal birds ." Mr. John Murray, on the other 

 hand, thinks the only use of the light is either as a 



* Journal of a Naturalist, p. 294. f Ibid. p. 293, 



J See Insect Transformations, pp. 34 and 141. 

 Intr.ii.411. 



