June is the month that fireflies come out and glow at night in Ohio.  They aren’t around for long.  I ran across this fellow while taking pictures of plants recently, and that got me to thinking.  I have fond memories from childhood about them- fireflies were pretty much magic to a kid.  Watching a yard-full of them flying in a leisurely manner, blinking in the twilight, is a classic summer experience.  I decided to read up on this intriguing insect, and I learned some surprising things.

Fireflies are a family of beetles that numbers 2,000 known species.  They produce an almost 100% efficient cold light bioluminescence which gives off no heat, mainly for the purpose of attracting mates.  They prefer moist and wooded environments, and are found on every continent except Antarctica.  Other names for fireflies include lightning bugs, golden sparklers, blinkies and moon bugs. is a great resource for all sorts of interesting facts about these insects.  For instance, I had no idea that fireflies spend most of their lives as larva and only spend a brief time in the classic firefly form that we know- only a few weeks.  The larva (who glow as well) spend a lot of time eating (earthworms and snails are on the menu) and then hibernate through the winter under tree bark.  In the warm weather, they change into a firefly, mate, lay eggs, and then die.

The flashes you see on warm summer nights are the culmination of their brief time as a beetle.  They accomplish this by combining 3 substances in their light organs, and produce particular flashing patterns, which vary by species.  Some fireflies also flash to warn others away, in a territorial fashion.   Interestingly, large masses of fireflies sometimes synchronize their flashes, which is a sight to behold, even attracting tourists to such annual events near Elkmont Tennessee and Congaree National Park in South Carolina.  One particular type of female firefly mimics the flashes of other firefly species- they attract an unsuspecting male, who is promptly eaten!

They are generally not tasty as prey, and their blood contains a bitter chemical that most animals avoid.  They engage in ‘reflex bleeding’ when attacked, giving the predator a yucky taste of what is to come if they decide to dine upon them.  That doesn’t sound that appetizing to me.

Unfortunately, the modern world’s light pollution is apparently disrupting the firefly’s mating signals, and this combined with habitat loss is leading to declining numbers of this insect.  However, there are things you can do to offer an attractive habitat for them.  Turning outside lights off, letting the grass grow higher, and leaving logs on the ground are positive steps one can take.

I think I’ll go out and look for that yellow glow when the sun sets this evening.