by Geoffrey Carpentier
I’ve noted, of late, a number of posts in some local Facebook groups expressing how happy folks are to see fireflies, as they fly around our yards on these warm summer nights! Few things in nature are so widely recognized and appreciated, but most people know little about them, except, they make us feel good. Over a decade ago, I wrote a column about fireflies, so I thought I’d revisit the subject, as many new readers have emerged and the appeal of the fireflies has not diminished.
Of all the summer nights I have enjoyed in my life, the ones where fireflies dance in the darkness are most pleasing. I’m not really sure why they bring me such pleasure but maybe it’s simply their ability to produce their own light (called bioluminescence). The light the adults and larvae produce is generated by enzymatic reactions within their abdomens which produce bioluminescence, in green, yellow or even pale red hues. This is amusing for us but is critical to their survival. The adults produce light to show they are looking for love. However, in addition to trying to attract mates, the adults produce light to defend territories and to warn predators. In many diurnal species, they don’t flash at all, as adults, but the larvae, sometimes called glow worms, do. The light, produced by these larvae, is not emitted to attract a mate but rather to warn off predators, telling them the larvae taste bad and are sometimes poisonous.
Once a mate is found, the adult female gets busy, as she lays her eggs just below the surface of the ground, in moist, wooded areas or near marshes. The eggs will hatch in 21 to 28 days and the larvae will feed until the end of summer, on the rotting leaves and forest floor litter. Larvae then overwinter here which can make them easy prey for predators.
Of the 2000 species of fireflies worldwide, 23 species can be found in eastern Canada. Most have similar behaviours and prefer the same habitats, damp woods near water. Their habitat is rich in prey, so they feast on worms, snails, other insects and even other fireflies. There is some uncertainty about their diet but it is believed some species don’t eat at all, as adults, while others may feed on pollen and nectar. Historically, fireflies inspired medical researchers, as the chemicals they use to produce the light were useful in the study of diseases, such as muscular dystrophy, diabetes and cancer.
Fireflies need darkness, so light pollution not only makes it hard for us to see them but for them to see each other. In fact, this and habitat loss are the two most critical reasons why their populations are declining worldwide. So, when the light gets too bright or the habitats are gone, why don’t they just move on to the next darkened habitat? Well, it has to do with their innate behaviour. Fireflies are home-bodies. They are born and die within a few meters of their natal forest, so by the time they figure out there’s an issue, it’s too late.
Another contributing factor is, their light, to be most effective, must be produced and responded to in a specific sequence. Studies show the sequence is disrupted when intense external flashes of light, such as passing cars, are encountered. Tiny influences, such as this, can have devastating impacts during their brief breeding season.
As a kid we caught them and the population seemed unaffected, or was it? I do recall many of my ‘lightning’ bugs died in the jars but as kid I didn’t know any better. So maybe catching them was a bad idea.
Please do your best to keep your outside lights off, during June and July, to give them the best chance of finding a mate. In addition, try to encourage and retain the moist woods and ponds near your home if you can. So, now is the time to see these wonderful insects, just find a quiet, dark place and enjoy these tiny beacons of light in the night. You won’t be disappointed!
Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff on-line on LinkedIn, Facebook and Instagram.