132 
EN TOMOLOGY 
undergoes rapid combustion in the rich supply of oxygen fur- 
nished by the trachez. 
The rays emitted by the common fire-flies are remarkable in 
being almost entirely hght rays, with almost no thermal or 
FIGs 1607: 
7 
oma 
eS 
rane 
pr ele 
me U 
St 
=F.) 
stot 
system of an insect. a, 
Tracheal an- 
tenna; b, 
b, palpus; s, 
stigmatal, branch; ¢t, main tracheal trunk; 
v, ventral branch; zs, visceral branch.— 
After Kose. 
brain; J, leg; , nerve cord; 
spiracle; st, spiracular, or 
actinic rays. According to 
Young and Langley, the radia- 
tions of an ordinary gas-flame 
contain less than three per cent. 
of visible rays, the remainder 
being heat or chemical rays, of 
no value for illuminating pur- 
poses; while the hght-giving 
efficiency of the electric arc is 
only ten per cent. and that of 
sunlight only thirty-five per 
The light of the fire- 
fly, however, may be rated at 
Cent. 
one. hundred per cent.; this 
light, then, is “pertect, and as 
yet unapproached by artificial 
means. , 
As to the use of this lumi- 
there is a_ general 
opinion that the light exists 
of sexual 
held by 
the author in regard to Pho- 
nosity, 
for the purpose 
attraction—a __ belief 
tinus, at least. Another view 
is that the light is a warning 
signal to nocturnal birds, bats 
or other insectivorous animals; 
this is supported by the fact 
that lampyrids are refused by birds in general, after ex- 
perience; young birds readily 
snap at a fire-fly for the first 
time, but at once reject it and thereafter pay no attention to 
these insects. 
