A reader posted a comment that requested, “Tell us more about glowworms!!” So, Clare… here goes…
Fireflies aren’t flies at all; they are beetles. Like all beetles, they undergo complete metamorphosis – a 4-stage lifecycle. Eggs are laid in the soil in summer. Larvae hatch and are active on and underground until the following spring when they will pupate. Because the larvae, like the adults, are luminous, they are called glowworms. Sometimes eggs, and adult wingless females (of some species – others have winged females) will also be called glowworms. Adults emerge in summer to mate and lay more eggs.
Classified under the Lampyridae family, there are around 200 species of fireflies in North American, and over 2,000 worldwide. Most of the U.S. fireflies seem to be found east of Kansas. Interestingly, there are some species in this family that are diurnal, rather than nocturnal and therefore are not bioluminescent. The photo here is from Seabrooke’s Flickr site. She wrote about these diurnal fireless fireflies in her blog in March. Sometimes called Winter Fireflies, these critters overwinter as adults rather than as larvae and are often seen on the bark of trees on winter days – if the sun shines warmly enough.
In species that are bioluminescent, there are special light-producing organs in the abdomen that contain “photocytes” – light-producing cells.
The light is created when oxygen combines with a substance called luciferin in the presence of the enzyme luciferase, in special cells called photocytes. – Dan and Susan Mahr
Or, if you want a really scientific explanation, check the link below called Nitric Oxide and Firefly Flashing!
Here’s a great photo from Jenn Orth’s Flickr site showing an adult’s abdomen where the light is produced:
The flashing patterns of the various species make for interesting studies. Scientists have found that yes, fireflies use their flashing lights to attract mates… But in some species, the females have developed the ability to mimic the flash pattern of other species and thus lure unsuspecting males. The poor deceived fellows become lunch.
We won’t be seeing adults for a few months around here where I live… But boy, when summer comes, the fields are just a-glitter with them. In the meantime, I’ll keep my eyes on the ground for glowworms!
- Firefly Profile – Minnesota DNR
Fireflies – Dan and Susan Mahr, University of Wisconsin – Madison
- Nitric oxide and Firefly Flashing – several authors at Tufts University
- Firefly Science – Links to all kinds of scientific articles, like the one above.
Firefly Lights – by Firefly Magic (you gotta have some of these for your garden! Audubon used them in an exhibit a while back… very cool!)
Update 5/12/2013: A reader let me know that the term glowworm means different things in different parts of the world. Scroll down to see John’s comment and learn more, and be sure to visit his website, too: http://www.firefliesandglow-worms.co.uk/