Beetles 
269 
The fireflies are familiar insects which are not flies but beetles, although 
their soft body and flexible leathery wing-covers are not of the typical 
coleopterous type. The nocturnal fireflies and their diurnal first cousins, 
the soldier-beetles, compose a coleopterous family, Lampyridas, of con¬ 
siderable size and common distribution over the whole world. The “glow¬ 
worm” of England and Europe is the wingless female of a common firefly, 
and the railway-beetle of Paraguay, a worm-like creature 3 inches long, 
that emits a strong red light from each end of the body and a green light 
from points along the sides, is also probably the wingless female of a large 
firefly species. In this country over 200 species of Lampyridae have been 
found. Comparatively few of them, however, are luminous. The light¬ 
giving organ is usually situated just inside of the ventral wall of the last seg¬ 
ments of the abdomen, and consists of a special mass of adipose tissue richly 
supplied with air-tubes (tracheae) and nerves. From a stimulus conveyed 
by these special nerves oxygen brought by the network of tracheae is released 
to unite with some substance of the adipose tissue, a slow combustion thus 
taking place. To this the light is due, and the relation of the intensity or 
amount of light to the amount of matter used up to produce it is the most 
nearly perfect known to physicists. 
Not only are the adult fireflies 
luminous, but in some species the 
pupae and larvae and even the 
eggs emit light. The combustion 
in the egg is of course accom¬ 
plished wholly without tracheae 
or controlling nerves. 
The larvae (Fig. 370) of Lam¬ 
pyridae mostly burrow under¬ 
ground, where they feed on soft- 
bodied insects, slugs, and other 
similar food. The adults, too, 
are carnivorous, the diurnal forms, 
called soldier-beetles, being com¬ 
monly seen on flowers or tree-trunks hunting prey. 
The commoner luminescent fireflies, or “lightning-bugs,” belong to the 
genus Photinus. P. pyralis, the common species from Illinois south, is 
\ inch long, blackish, with prothorax with red disk, yellow margin, and black 
spot in center, and the elytra with narrow yellowish border. Farther north 
and east the commonest species is P. scintillans (Fig. 371), similar in mark¬ 
ing but smaller. P. angulatus, \ inch long, is pale, with wide yellow margins 
on elytra and the margin of the prothorax clouded with black. The com¬ 
moner soldier-beetles belong to the genus Chauliognathus, which is char- 
Fig. 370. Fig. 371. Fig. 372. 
Fig. 370.—Larva of firefly, Photinus modestus. 
(Twice natural size.) 
Fig. 371.—Firefly, Photinus scintillans. (Three 
times natural size.) 
Fig. 372.—Checker-beetle, Trichodes ornatus. 
(Twice natural size.) 
