170 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 Asilide 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 heht 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 
to detect it domg anything in the evening beyond 
flitting aimlessly about, like house flies in a room, 
hovering and revolving in company by the hour, 
apparently foramusement. Thus, the more closely 
we lock 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 
