The magic of fireflies

As most people in Hermanus will know by now, October is firefly time. That’s when the magic happens – or rather, the brief, three-week mating season when flashes of light can be seen in undisturbed habitats like the fynbos. These are fireflies out on the town.

A synchronous firefly. PHOTO: firefly.org

Let’s start with a brief description of the fireflies of the Western Cape. We have one species, Luciola capensis – just one of about 30 southern African species and 2 000 species of fireflies world-wide. Fireflies are neither flies, nor on fire. They are actually beetles (Coleoptera), belonging to the family Lampyridae. Some firefly species are quite large – up to 2.5 cm. Our local L. capensis is tiny – about the size of a grain of rice.

Metamorphosis

As is the case with all insects, fireflies go through metamorphosis. Eggs are laid in spring and hatch into larvae that live in damp soil or leaf litter over the summer and most of the winter. 

Lampyrid firefly larva eating a snail.
PHOTO: Paul, Flickr

At the end of winter the larval form pupates. The most amazing change occurs during pupation. The cells that made up the larva dissolve into a soup and then reassemble gradually to turn into an adult insect. After about three weeks, the adult fireflies emerge. Adults mate and lay more eggs and the cycle goes on. 

Metamorphosis is very advantageous to insects as the two distinct forms of larva and adult have quite different functional lifestyles. 

A firefly larva is a voracious predator of all things slimy in the leaf litter such as worms, slugs and snails. The larva has a vicious bite, injects digestive enzymes into its prey and slurps up the liquefied “smoothie”. This allows it to predate on prey much larger than itself.

While firefly larvae live to eat, thus building up stored energy resources for their adult lives, the adults generally don’t bother to eat, but live only to fly around to find a mate to procreate. 

Matchmaking by night 

Flying around in daylight has its drawbacks for an insect. For a start, there are more predators around, so many species of fireflies have taken to matchmaking by night. The problem is that it’s rather more difficult to find a mate in the dark, so these nocturnal fireflies have evolved a solution to that dilemma – they make their own light through a process called bioluminescence. 

Fireflies enjoy the open air as the sun goes down.

Bioluminescence is a “cold” light produced in a special light organ in the terminal segments of the insect’s abdomen. Both males and females use light. Sometimes even the larvae will emit a steady light to warn predators that they are toxic and not good to eat, leading to the misnomer ‘glow-worms’. 

Bioluminescence is produced by a chemical reaction between a molecule called luciferin, oxygen and an energy source called ATP. This reaction is catalysed by an enzyme called luciferase. Basically the end result of this reaction is the production of a photon of light. Most fireflies don’t emit a steady light, but can turn the light on and off to produce a flash pattern that is unique for each species. The mechanism for flashing is controlled by the same substance (nitric oxide) that is produced by Viagra.

L.capensis firefly. PHOTO: Terry Priest

Fireflies light up for a variety of reasons, but the main reason is to find a mate. Females sit low down in the vegetation or on the ground and wait for a male to fly by. If she likes his flashing, she will return the flash as a ‘come-hither’ signal. After mating, the female will lay her eggs in damp soil or leaf litter and then both adults die – destiny fulfilled. 

Firefly society has its femmes fatales. The female of one species of firefly can imitate the flash pattern of the females of another species. When the targeted male approaches, hoping to make a liaison, she eats him. Such is life – or rather, death.

Shine your light on me

If you want to encourage firefly magic in your garden, here are a few things to remember: 

  • Switch off all external lights. Light pollution and loss of habitat are the two main reasons why we don’t see many fireflies. Artificial light confuses them. 
  • Do not use snail bait, insecticides or chemicals in the garden. 
  • If your dog is on a systemic tick/flea product like Bravecto, be extra careful. The active ingredient that kills ticks and fleas on your dog is excreted unchanged in the dog’s poo. Burying it in the garden or leaving it around will kill the desirable soil insects in your garden – including dung beetles and fireflies.  Rather pick up the poo and flush it down the toilet.  
  • Leave your soil undisturbed since the larvae spend most of the year in the soil and tilling it will kill them. Rather just add more mulch. If you want wildlife in the garden, leave it to nature.

About the Author

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Whale Coast Conservation passionately lives by its slogan “Caring for your environment”.

Its small staff and volunteers are dedicated to

  • raising community and visitor awareness of the unique, biodiverse natural resources of the Cape Whale Coast region and
  • to projects that convert awareness into practical actions that lead towards living sustainably.

WCC ensures expert representation in public participation processes that contribute to environmental and developmental policies and legislation.  We monitor regional development; and ensure compliance with legislation and guidelines.

WCC increases general public awareness of sustainability through environmental education, citizen-science research projects, community projects and campaigns.

WCC communicates with its audience through exhibitions, signage, technology demonstrations, workshops, talks, film shows, newsletters and articles.

WCC places emphasis on educating future generations through its Youth Environment Programme (YEP).  YEP is offered to 24 schools in its target area with a total of over 10,000 learners.

WCC facilitates schools’ participation in special events such as Earth Day, Walking for Water, Arbor Day and Coastal Clean-ups.

WCC facilitates educator development programmes to improve the capacity of educators to offer informed environmental content in their lessons across all learning streams.

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