to some American species of Lampyris. 121 



This part is covered by two scuta of a pale or whitish 

 straw-colour, and transparent. These scuta, like almost 

 every other part of the insect, are covered with pili, or 

 villi : but here this villous covering is fine, and requires 

 the aid of a strong double microscope to render it visible. 



Each scutum has a small black spot on each side of 

 a line, which divides the abdomen longitudinally. These 

 spots, when viewed through a common magnifying 

 glass, appear to be perforations, and as such I considered 

 them, at first : but, upon examining them with a very 

 strong double microscope, I could not perceive that they 

 were such. 



The Lampyris certainly respires as other insects do, 

 by means of spiracula : and I was, for some time, in- 

 clined to believe, that these spots were perforations for 

 the admission of air, and thence produced the light ; for 

 I shall, presently, show, that the air taken in by the spi- 

 racula has no communication with the luminous part. 



The insect has the power of remaining opake for any 

 length of time : but if that part of the luminous portion, 

 which is covered by the terminating scutum, be cut in 

 two, without injuring the other, it instantly becomes bril- 

 liant, and remains so ; the insect not having power to 

 increase or to diminish the lustre. But the other scutum 

 is not, in the least, affected. It is opake, or nearly so 

 (that is, perfectly natural), except when the insect exerts 

 its voluntary power of giving out light, and then it pre- 

 sents the same appearance that it did previously to the 

 mutilation. 



