CH.V1I.] LUMINOUS WINGED INSECTS. 121 



extensile ; one or two being frequently stretched 

 beyond the line of the others. It was not long be- 

 fore I convinced myself that this singular instru- 

 ment was employed by the insect for cleaning 

 itself, and it would have been difficult to devise any 

 thing more effectual for the purpose, though its ac- 

 tions were different from all others of this kind with 

 which I was acquainted, inasmuch as it operated by 

 suction, and not as a comb, a brush, or a wiper. It 

 was moreover furnished in the interior with a sort 

 of pocket of a funnel shape, formed by the conver- 

 ging rays, into which was collected the dirt, &c., 

 from off the back of the insect." The accuracy of 

 these facts we must leave for further investigation. 

 After the space of one year and nine months the 

 larvae are changed, having however frequently cast 

 off their skins, into the second or pupa state, in 

 which they remain nearly quiescent for two or 

 three weeks, when they change their last skins and 

 become perfect insects. In this state the two 

 sexes are easily distinguished, as the male appears 

 like a perfect beetle, having wings and wing-cases ; 



while the female, on the contrary, seems to have 

 undergone hardly any change in appearance from 

 that of the larva, except that she is much larger, and 

 of a lighter colour. It is the female which is prin- 

 cipally luminous in the perfect state. The male 

 was generally considered incapable of exhibiting 

 any light, until John Ray, the father of English 

 naturalists, first pointed out that the latter sex was 

 VOL. II. L 



