Author Archives: Sara Lewis

The Winter Firefly

Hey, surprise! Some adult fireflies never.even.light.up 😳.

Yeah, I know it sounds weird. Yet based on shared ancestry (including their bioluminescent larvae), these so-called “dark” fireflies are authentic card-carrying members of the family Lampyridae. Common from coast to coast, each spring they quickly dominate the iNaturalist observations that show up in our Fireflies of the USA and Canada project.

Winter fireflies range 6-16 mm long

One of my personal favorite creatures happens to be the winter firefly, Ellychnia (ee-lick-ne-ah) corrusca, a species complex that’s widespread across eastern North America from Florida to Ontario. (In all, there are 12+ species in the genus Ellychnia, including several species found just on the west coast – reference below).

Easy to recognize, our eastern Ellychnia corrusca adults sport oval-shaped bodies, entirely dark wing covers (no pale margins), and a distinctive color pattern on their pronotum: a big central black spot is edged with red and enclosed within two pale parentheses.

Winter fireflies earn their common name from the fact that their adults can survive sub-freezing temperatures. Each fall in New England they gather on particular trees – they seem to frequent the same trees year after year – where they wedge themselves into grooves and hunker down to spend the winter. And they are decidedly hardy – in Massachusetts, Jen Rooney and I did a mark-recapture study and found 90% overwintering survival!

Last May this pair stayed together on my window screen for 17 hours.

In early spring, just when the maple trees begin flowering, winter fireflies start crawling up tree trunks. As temperatures rise, they begin flying through forested habitats in search of mates. Pairs mate in tail-to-tail position,  then the female flies off to lay her eggs. 

Like all fireflies, Ellychnia larvae are carnivorous. Rarely seen, they live and hunt within decaying wood. Hatching out in early summer, these larvae will spend the next 16 months eating and growing. Not until late summer of their second year will they transform into adults, which gather again on trees to overwinter.

 WIthout any lanterns, distinguishing between an Ellychnia female and a male requires a pretty close look at the underside of their abdomen. In females (below right), the last segment is triangular with small notch ; in males (below left), this segment is rounded and unnotched.

Personally, I don’t even care that they don’t light up – I love greeting these dark fireflies each spring! After a long winter, they bring a welcome promise of warm summer nights & lights ahead. So keep your eyes peeled and enjoy these unusual fireflies!

Further reading?

Jen Rooney & Sara Lewis, 2000. Notes on the life history and mating behavior of Ellychnia corrusca. Florida Entomologist 83: 324-334.

Kenneth Fender, 1970. Ellychnia of western North America. Northwest Science 31-43.

      

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What’s behind a fabulous firefly season?

Sometimes our summer nights are ablaze with silent sparks, while other years we might barely see a flash in the exact same spot. What gives? A recent study provides some insight into what drives these fluctuations, and it reminds us to take the long view.

These flashy adults are the just reward for having survived many months during their larval stage.

Keep in mind that the flashy adult represents just a tiny fraction of a firefly’s life cycle. Before that, they spent up to two years living underground in a juvenile larval stage. During this time they are eating machines, growing steadily as long as they have access to their prey – mainly earthworms, snails, and slugs. Only if they manage to survive predators, competitors and climatic conditions will they eventually emerge into an adult firefly.

Fireflies spend many months being very cute in this larval stage

The study:

Firefly Watch observations gave info on firefly abundance across all species

What was their goal? Tracy Evans and her colleagues (see full citation below) decided to see if they could predict changes in adult firefly abundance across different U.S. locations using data on weather conditions during juvenile development.

What did they do? They took data gathered by citizen scientists who participated in Firefly Watch between 2008 and 2016 (only total firefly counts were used in this study). They combined this with information from NOAA on monthly temperature, precipitation (rain & snowfall) and soil moisture for each location.

Weather conditions before adult emergence had an impact on firefly abundance.

What did they discover? Weather conditions during juvenile development had a small but significant effect on the abundance of adult fireflies. In particular, adult abundance increased when soil moisture was high during development, and decreased when soil moisture was low. Precipitation also mattered: for 20 months before adult emergence, both too much and too little precipitation reduced firefly abundance. Very high maximum temperatures during the previous winter and spring reduced abundance.

What does this mean? Of course different firefly species will have different requirements, but this study reveals some interesting general patterns. Fireflies seem to thrive when there’s sufficient soil moisture, and when there’s just enough precipitation – not too much and not too little during their juvenile stages.

Citation (warning, paywall!): Evans, Tracy R. ; Salvatore, Donald ; Van De Pol, Martijn ; Musters, C. J. M. 2019. Adult firefly abundance is linked to weather during the larval stage in the previous year. Ecological Entomology, 44: 265-273.

Happy Mother’s Day, Blue Ghost Mamas!

This wingless female is packed full of eggs

Let’s face it. Every single lightningbug out there is desperately trying to pass on its genes to the next firefly generation. But some female glow-worms are really dedicated mothers, so I think they deserve a special shout-out today.

Photo by Lynn Faust
Blue ghost females shine like tiny jewels

Like other glow-worms, females of the Blue Ghost firefly are born wingless, so they can only dream of flying. Instead, they’re destined to spend their nights crawling around the leaf litter, shining from tiny glow spots, hoping to attract a mate. However, because they’re freed from the hefty demands of flight, glow-worm females can channel all their resources into making lots of eggs – like the female pictured above!

After she has mated, the Blue Ghost female lays a batch of about 30 eggs down in the leaf litter. Then she curls her body, guarding her eggs and glowing protectively above them until she dies.

This egg-guarding behavior is highly unusual for fireflies. Although she won’t live to see her offspring hatch (that will take about a month), she can die happy knowing she’s given her offspring the best possible start in life!

So Happy Mother’s Day to all the Blue Ghost mamas!

Egg-guarding by a blue ghost female firefly

Learn more about female glow-worms in Silent Sparks Chapter 5: Dreams of Flying.

You can read our article about courtship and mating behavior in Blue Ghost fireflies here.

They Be Drowning in Light

Bright nights are making it hard for glow-worms to find a mate (female Lampyris noctiluca; photo by John Tyler)

Glow-worms & fireflies are uniquely susceptible to light pollution because our bright nights interfere with their ability to find mates. Fiona Benson’s poem beautifully captures the urgency of female glow-worm – “come find me – it is time – and almost dawn’ – and the male’s dilemma:

“all night he looks for her in petrol stations
villages and homesteads, the city’s neon signs:
where are you – it is time – and almost dawn.”

Love Poem, Lampyridae (Glowworms) by Fiona Benson

The female born again with little changed
except she has no mouth and may not eat,
except she has this urge to climb, and a light
she must raise and twist; the male born again
with little changed except he has no mouth,
except he has this urge to search, and wings –
oh she must twist and turn her tail’s green fire
like bait, its little stab of brightness in the night,
and he must search with wings through
    troubled air
to find her pinhole lure, its single, green,
seducing star …. All night she signals him in:
come find me – it is time – and almost dawn;
all night he looks for her in petrol stations
villages and homesteads, the city’s neon signs:
where are you – it is time – and almost dawn….

Once were humans wandered in the lanes,
led astray by fairies, foxfire, who found
their stranger selves and brought them home

Now the dark is drowned, but some things
you can only find beyond the light,
and it is time and almost dawn and love,
my love, there is no finding then.

Published in The Guardian, part of Carol Ann Duffy’s poetry collection celebrating the beauty of a vanishing insect world.


Firefly Wonder in Zanzibar

From Paul Saltzman, in Oakville, Ontario –

As a filmmaker, I’ve had many grand experiences of nature: 8 days of floating down the Colorado River through the Grand Canyon, every second bringing a new vision of beauty; flying over the Amazonian watershed,  trees so thick you couldn’t see the ground but the sun glistened beneath the trees because water entirely covered the  forest floor. And then there was Zanzibar….

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A Guide to Lightningbug Linguistics

Ever wish you could understand what the fireflies are saying? Well, you now can!

The fireflies you’ll see most often in the eastern United States belong to one of the 34+ species of Photinus lightningbugs. These familiar fireflies fill our summer evenings with delight – they’re easy to catch because they fly at a leisurely pace, low above the ground. During summer months, different species make brief appearances, each with a mating season that lasts only a few weeks. Different Photinus species also start their courtship flashing at different times of night: certain species court just at dusk, while others wait until full darkness.

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What kind of firefly am I?

People have been posting their firefly photos to the community science site iNaturalist – it’s wonderful! Inspired by everyone else’s fabulous shots (I wish I could do that with my iPhone), here’s a short key to help you distinguish six of the most common firefly genera found in the U.S. Give it a try & let me know what you think in the comments below!

1a. Active during evening or nighttime, abdomen with a lantern, wing covers without pale borders ……. Go to #2

1b. Active during daytime, abdomen without a lantern, wing covers with pale borders ……. Go to #4

2a. Pronotum (head shield) with a raised ridge running down the midline & angular outline ….. I am Pyractomena (18 species)

2b. Pronotum without a raised ridge running down the midline (could be flat or grooved), outline more round in shape ……. Go to #3

3a. Legs are long  (almost as long as the wing covers) and slender; when beetle is viewed from the side, the front corner of each wing cover curls smoothly under, making its shoulders look hunched ….  I am Photuris (73 species)

3b. Legs are short (less than half as long as the wing covers) and stout; when shoulder is viewed from the side, the wing cover’s sharp edge makes a straight line …. I am Photinus (48 species)

4a. Antennae inconspicuous; threadlike and short …. Go to #5

4b. Antennae conspicuous; flattened, long and saw-toothed I am Lucidota (4 species)

5a. Largish beetle (length 1cm or more)I am Ellychnia (12 species)

5b. Tiny beetle (length ≤ 5 mm) …. I am Pyropyga (4 species)

Other Online Resources

Key to Fireflies of Ontario by Stephen Luk, Stephen Marshall and Marc Branham (2011)

Photinus flash codes