250 COLEOPTERA CHAP. 



that the female is of the utmost rarity, though the male is not 

 uncommon. 



The nature of the luminosity of Lampyris has given rise 

 to many contradictory statements ; the light looks somewhat 

 like that given off by phosphorus, and is frequently spoken of 

 as phosphorescence ; but luminescence is a better term. The 

 egg, larva, pupa, and male are luminous as well as the female 

 (at any rate in L. noctilma^) ; the luminescence is, however, most 

 marked in the female imago, in which it is concentrated near 

 the extremity of the abdomen ; here there are t\vo strata of 

 cells, and many fine capillary tracheae are scattered through the 

 luminous substance. Wielowiejski concludes that the light- 

 producing power is inherent in the cells of the luminous organ, 

 and is produced by the slow oxidation of a substance formed 

 under the influence of the nervous system. The cells are 

 considered to be essentially similar to those of the fat-body. 1 

 The luminescence of Lampyridae is very intermittent, that is to 

 say, it is subject to rapid diminutions and increases of its 

 brilliancy ; various reasons have been assigned for this, but all 

 are guesses, and all that can be said is that the changes are 

 possibly due to diminution or increase of the air-supply in the 

 luminous organ, but of the way in which this is controlled there 

 seems to be no evidence. Considerable difference of opinion has 

 existed as to the luminescence of the eggs of Lampi/ris. If it exist 

 in the matter contained in the egg, it is evident that it is 

 independent of the existence of tracheae or of a nervous system. 

 Newport and others believed that the light given by the egg 

 depended merely on matter on its exterior. The observations of 

 Dubois ' 2 show, however, that it exists in the matter in the egg ; 

 he has even found it in the interior of eggs that had been 

 deposited unfertilised. 



From time to time, since the commencement of the nineteenth 

 century, there have appeared imperfect accounts of extraordinary 

 light-giving larvae found in South America, of various sizes, but 

 attaining in some cases a length, it is said, of three inches ; they 

 are reported as giving a strong red light from the two extremities 

 of the body, and a green light from numerous points along the 



1 Zcitschr. iviss. Zool. xxxvii. 1882, p. 354 ; also Emery, op. cit. xl. 1S84, 

 p. 338. For another theory as to the luminescence, see p. 259. 



2 Bull. Soc. Zool. France, xii. 1887, p. 137, postea. 



