ioo CRUISE OF THE BARRERA 



this perfection of economy in the production of 

 a light, the actual candle-power of the light is 

 extremely low. On account of its rays being con- 

 fined to green in the spectrum, the light emitted 

 would be of little use as an illuminant, for it would 

 distort all objects not of green color. The eye 

 is most sensitive to green, and the firefly having 

 produced a light that is restricted to the green 

 spectrum has succeeded in producing a perfect 

 light to be seen, but not a good light for the 

 illumination of objects. But such is obviously not 

 the purpose of the glow. It is almost certainly for 

 sexual attraction of other individuals of the species. 



This beetle has the curious habit of all chick- 

 beetles of "snapping" by a convulsive muscular 

 movement causing it suddenly to leap without 

 employing either legs or wings. The elfin beauty 

 of the moving lights through the woods or over 

 the fields is very pleasing to the sight and inclines 

 one to accept again his childhood theories concern- 

 ing fairies. 



The party remaining on board devoted the day 

 to a thorough examination of the shallow waters 

 along the mainland shore and within the small 

 lakes of the mangrove shore belt. The dredgings 



