406 LUMINOUS INSECTS. 



being the sexes of the same insect. In the course of 

 our inquiries you will find that sexual differences even 

 more extraordinary exist in the insect world. 



It has been supposed by many that the males of the 

 different species of Lavfpyris do not possess the property 

 of giving out any light ; but it is now ascertained that 

 this supposition is inaccurate, though their light is much 

 less vivid than that of the female. Ray first pointed out 

 this fact with respect to L. noctiluca*. Geoffroy also 

 observed that the male of this species has four small 

 luminous points, two on each of the two last segments 

 of the belly 5 : and his observation has been recently 

 confirmed by Miiller. This last entomologist, indeed, 

 saw only two shining spots ; but from the insect's hav- 

 ing the power of withdrawing them out of sight so that 

 not the smallest trace of light remains, he thinks it is 

 not improbable that at times two other points still smaller 

 may be exhibited, as Geoffroy has described. In the 

 males of L. Splendidula and of L. hemiptera the light is 

 very distinct, and may be seen in the former while fly- 

 ing c . The females have the same faculty of extinguish- 

 ing or concealing their light a very necessary provi- 

 sion to guard them from the attacks of nocturnal birds : 

 Mr. White even thinks that they regularly put it out 

 between eleven and twelve every night d : and they have 

 also the power of rendering it for a while more vivid 

 than ordinary. 



Authors who have noticed the luminous parts of the 

 common female glow-worm, having usually contented 

 themselves with stating that the light issues from the 



* Hist. Ins. 81. " Hut. abreg. i. 168. 



e Illiger Mag. iv. 195. * Nat. Hist. ii. 279. 



