1 70 The Naturalist in La Plata. 



not so squeamish, and devour them readily, just as 

 they also do the blister-fly, which one would imagine 

 a morsel fitted to disagree with any stomach. One 

 of their enemies is the Monedula wasp ; another, 

 a fly, of the rapacious Asilidge family ; and this fly 

 is also a wasp in appearance, having a purple body 

 and bright red wings, like a Pepris, and this mimetic 

 resemblance doubtless serves it as a protection 

 against birds. A majority of raptorial insects are, 

 however, nocturnal, and from all these enemies that 

 go about under cover of night, the firefly, as Kirby 

 and Spence rightly conjectured, protects itself, or 

 rather is involuntarily protected, by means of its 

 frequent flashing light. We are thus forced to the 

 conclusion that, while the common house fly and 

 many other diurnal insects spend a considerable 

 portion of the daylight in purely sportive exercises, 

 the firefly, possessing in its light a protection from 

 nocturnal enemies, puts off its pastimes until the 

 evening; then, when its carnival of two or three 

 hours' duration is over, retires also to rest, putting 

 out its candle, and so exposing itself to the dangers 

 which surround other diurnal species during the 

 hours of darkness. I have spoken of the firefly's 

 pastimes advisedly, for I have really never been able 

 t o detect it doing anything in the evening beyond 

 flitting aimlessly about, like house flies in a room, 

 hovering and revolving in company by the hour, 

 apparently for amusement. Thus, the more closely 

 we look at the facts, the more unsatisfactory does 

 the explanation seem. That the firefly should have 

 become possessed of so elaborate a machinery, pro- 

 ducing incidentally such splendid results, merely as 



