D&D Basic Monsters: Giant Fire Beetle.

It may be giant, but it's still small.

In the original Monster Manual, gan beetles were quite abundant, including the Giant Stag Beetle, Giant Boring Beetle, the Giant Bombardier Beetle, the Giant Rhinoceros Beetle, the Giant Water Beetle and of course the Giant Fire Beetle. So far in fifth edition, the Giant Fire Beetle is the only survivor.

Despite its name, the Giant Fire Beetle has no special fire related attacks or defenses, but it lets of nice pleasant light at least.

Like most giant species, the Fire Beetle has a real life counterpart (or a whole family of them to be precise, the Pyrophorus) native to central and southern America. These beetles, about one inch in length, probably use their bioluminescent lights to attract insects for food.