Nature's Night Lights. \ 69 



standing this fact, and assuming that we have here 

 the whole reason of the existence of the light- 

 emitting power, a study of the firefly's habits com- 

 pels us to believe that the insect would be just as 

 well off without the power as with it. Probably it 

 experiences some pleasure in emitting flashes of 

 light during its evening pastimes, but this could 

 scarcely be considered an advantage in its struggle 

 for existence, and it certainly does not account for 

 the possession of the faculty. 



About the habits of Pyrophorus, the large tropical 

 firefly which has the seat of its luminosity on the 

 upper surface of the thorax, nothing definite appears 

 to be known ; but it has been said that this instinct 

 is altogether nocturnal. The Pyrophorus is only 

 found in the sub-tropical portion of the Argentine 

 country, and I have never met with it. With the 

 widely-separated Cratomorphus, and the tortoise- 

 shaped Aspisoma, which emit the light from the 

 abdomen, I am familiar; one species of Crato- 

 morphus a long slender insect with yellow wing- 

 cases marked with two parallel black lines is " the 

 firefly " known to every one and excessively abun- 

 dant in the southern countries of La Plata. This 

 insect is strictly diurnal in its habits as much so, 

 in fact, as diurnal butterflies. They are seen flying 

 about, wooing their mates, and feeding on composite 

 and umbelliferous flowers at all hours of the day, 

 and are as active as wasps during the fall glare of 

 noon. Birds do not feed on them, owing to the 

 disagreeable odour, resembling that of phosphorus, 

 which they emit, and probably because they are 

 found to be uneatable ; but their insect enemies are 



