July, 1892. 
THE NATURALIST IN LA PLATA. 
151 
its bosom, while with the other it seized the head, and, giving 
it a violent wrench, dislocated the neck. The colt fell to the 
earth as if shot, and he affirmed that it was dead before it 
touched the ground.” 
What follows tells us something about fireflies:—“ By 
bringing a raptorial insect and a firefly together, we find that 
the flashing light of the latter does actually scare away the 
former, and is, therefore, for the moment a protection as 
effectual as the camp fire the traveller lights in a district 
abounding with beasts of prey. Notwithstanding 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 compels 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 Pyropliorus, 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 Pyropliorus 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 Cratomorphus—a long slender insect 
with yellow wing-cases marked with two parallel black lines— 
is the “ firefly ” known to everyone and excessively abundant 
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 full glare of noon. Birds 
do notfeed 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 
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 Asilidse 
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 
