Tag Archives: larvae

Next up: Fall glow-worm extravaganza

Autumn happens to be quite an exciting time for fireflies. But, yeah I get it – you probably can’t imagine fireflies beyond summer.  After all, that is when adult get all reproductive and stuff. But there’s cryptic chapter in the firefly’s life story, and it’s starting right now.

Firefly Life Cycle.png

Once mated, the female firefly will produce 30-100 eggs, laying them one-by-one in some moist dirt or moss. After a few weeks, these eggs hatch out into tiny larvae that immediately burrow down underground. Though adult fireflies only live a few weeks, their progeny will spend up to two years hanging out underground.

Larval Jaws

photo by Melvyn Yeo (Flickr)

Baby fireflies happen to be voracious predators. They’re constantly on the hunt for earthworms, snails, and any other soft-bodied prey. They attack creatures that are much bigger than themselves. How do they manage this? First, they use their sharp, sickle-shaped jaws to inject the prey with paralyzing neurotoxins. Next, they secrete digestive enzymes to liquify their prey, then they slurp it up. Earthworm smoothie, anyone?

When they’re disturbed, larval fireflies glow from two tiny lanterns located at the tip of their abdomen. All firefly larvae can light up, across 2000+ species, even when the corresponding adults cannot. So we think fireflies’ light-producing talent first evolved because it gave these juveniles some advantage.

But … what’s the point of these juveniles being so conspicuous?

We know that fireflies contain nasty-tasting chemicals that help them avoid getting eaten (see earlier post). Lots of poisonous creatures use bright coloration to warn off potential predators. Yet firefly larvae are mainly active at night or underground, where having bright colors would be futile. But a flash in the darkness would certainly do the trick – like a neon sign, it  blazes out “I’m toxic – stay away!”

So get ready to watch for firefly larvae crawling along roadsides and wooded paths, glowing dimly. Often overlooked, these juveniles should rightly be celebrated as the original inventors of fireflies’ magical lights.

pageofbats life cycle illustration

Illustration by pageofbats (Flickr)


Fall glow-worm season is here!

Each autumn the world seems aglow with foliage and jack-o-lanterns. But they’re not the only  glowing things lighting up this season. Fall is also a great time to spot the crawling, glow-in-the-dark stage that all juvenile fireflies pass through.

Firefly larvae and pupae

Glowing firefly larvae (left) and pupae (photo by Siah St. Clair)

Hatched from eggs laid during summer months, these firefly larvae can now be seen crawling along  roadsides or wooded paths, glowing dimly from two tiny lanterns.    Photuris and Pyractomena larvae are the two types seen most often in the U.S. But one reader in Portland, Oregon even spotted  the much rarer Douglas fir glow-worm, Pterotus, along a path in Mt. Tabor Park. Continue reading

About Those Firefly Babies…

Everyone loves fireflies and everyone loves babies, so it sounds like baby fireflies would be extra cute, right? But….


what they eat

Baby fireflies are voracious predators

Baby fireflies are ruthless carnivores dedicated to gluttony and growth. During their juvenile stage, most fireflies live in soil and rotting wood, where they prey upon earthworms, snails, and other soft-bodied creatures.

For the past several weeks, I’ve kept busy rearing 20 Lucidota firefly larvae. Just 5 weeks after they hatched out from eggs, my baby fireflies are growing fast. But I have to admit, watching them eat is getting scary! If you’ve seen Stranger Things, maybe you’ll know what I mean.

At rest, these babies huddle together. When I give them an earthworm they quickly gang up on it. This gregarious feeding habit lets them take down prey  much, much bigger than themselves. Using their sickle-shaped jaws, they inject the worm with paralyzing neurotoxins. Then, while it’s still alive, they cut it up it into pieces. Over the next 24 hours, they line up like suckling piglets to suck up their liquified prey.  Yum – nice fresh earthworm smoothie, anyone?

Anyway, each night before I go to bed, I now check to make sure my baby fireflies are securely inside their containers. So sweet dreams!




Raising Fireflies?!

As I’ve described previously in this blog, it’s generally proven difficult to raise U.S. fireflies. Once you’ve gotten the eggs to hatch, the next problem is getting the larvae to eat, grow, and survive. It sounds simple, but it takes young fireflies up to 2 years to develop. As their size increases, they need to shed their old exoskeleton & grow a new one. Each of these molting cycles is called an instar, and fireflies need to go through ~11 larval instars before they’re finally ready to metamorphose into the adults we’re familiar with.

So I’m really excited to report that so far I’ve had pretty good luck this year!

I’ve been caring for  ~20 very active Lucidota larvae that hatched from eggs. Now 2 weeks old,  they’re shown below climbing on a bit of earthworm poop. Because they’re still small, every few days I feed them cut-up pieces of earthworms (yuck). After enjoying a gluttonous feast last week, many have molted into a new instar.

Continue reading

Can I raise fireflies?

Because they have a complex life cycle, raising fireflies is very difficult. To get from egg to adult, you will need to work out conditions that promote survival not just for the eggs, but also the larval and pupal stages. So far, scientists have been able to successfully rear just a few Asian firefly species (Luciola cruciata, Aquatica lateralis, and Aquatica ficta), all with aquatic larval stages.

Many people (including myself, Jim Lloyd, Lynn Faust and Larry Buschman) have tried to raise U.S. fireflies  – all of which have terrestrial larvae – but without much success. If you find a mated female, it’s generally easy to get her to lay her eggs on moss. With luck, within a few weeks the eggs will successfully hatch out into tiny larvae. They’re cute and hungry! But the next step is extremely difficult: getting these larvae to eat, grow, and survive for the many months it takes before they’re big enough to pupate.

Although I’ve tried several different species, I’ve never gotten any of these terrestrial larvae to survive longer than 2-3 months. I’ve tried feeding them earthworms, snails, cat food (both wet and dry), and never gotten survival rates above 1%. So, as I recommend in Silent Sparks: Stepping Out, the best thing is to return any newly-hatched firefly larvae to their original habitat, where they’ll likely have a better chance of survival.

6 w share earthworm bit

At 6 weeks, only 1% of these Ellychnia larvae still survived.

If you’re still determined to give it a try, Terry Lynch’s Firefly Notebooks provide a lot of useful information; Terry also describes his techniques for rearing Photinus larvae here.

Update April 2017Exciting news – Dr. Scott Smedley at Trinity College, Hartford CT has successfully raised Pyractomena borealis fireflies for two generations! Stay tuned for more details about the rearing techniques he & his students have developed. 



Baby Fireflies @ Work

In the firefly life cycle, the adults we see flying around us represent just the tip of the iceberg. Adult fireflies only  live for a few weeks, but they spend up to two years in a juvenile larval stage. We don’t see much of them during this time because they live underground (or underwater, in certain species).baby firefly

During this larval stage baby fireflies concentrate on gluttony and growth, feasting on earthworms, snails, and whatever other soft-bodied prey they can find. They are small but fearsome predators, using their hollow, sickle-shaped jaws to inject their prey with paralyzing neurotoxins. Then they secrete digestive enzymes to liquify and ingest the prey while it’s still alive. Continue reading