Lighting-up Time

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There was a time when I lived in Vermont, one of the smallest states in the USA, located in the north-east of the country just below the Canadian border. One of the pleasures of summer was to sit in the screened-in porch, enjoying the evening air, but safe from incessant mosquitoes, and wait for the fireflies to come out. Imagine a gnat wearing an LED light and you’ve got a firefly. Only once night had fallen did the fireflies appear, dozens of dancing specks of light which lit the pitch-black garden like a party of Tinkerbells.

You’re unlikely to see ‘fireflies’ in England unless your neighbour has strung fairy-lights in the trees, but you might see a close relative – the glow-worm. Unlike those creatures where the male of the species uses a bit of flash to beguile a mate, with glow-worms it’s the female who goes all out to attract attention. While the males are winged with hard, beetle-like backs, the females look like larvae – soft as a marshmallow and wingless. So far, so unremarkable. But as the female spends her short life confined to a few metres of ground, and her day-time look is a discreet, subdued brown, Nature has given her a clever way to stand out. Thanks to a chemical reaction between oxygen in the air and enzymes in the glow-worm’s body, she can activate a ‘lantern’ in her abdomen and literally light up her rear end. This vivid green, pulsing bioluminescence can be switched on and off at will, either to attract a mate or to startle enemies.

Once a mate has been found, eggs are often laid on open ground, and the newly hatched larvae must crawl to the shelter of vegetation with due haste. With luck, they’ll reach a ready food supply of slugs and snails. Even the larvae can manage a brief glow, although it’s rather feeble compared to their mother, whose light can be seen up to 50 metres away.

Sadly, the population of glow-worms across Europe has declined over the last 70 years, but they can still be found in England on the chalky grassland of the Downs. Their habitat also includes hedgerows, railway embankments, heathlands and cliffs. People lucky enough to live in areas of low light pollution may come across them when walking in the countryside after dark. But they’ll have to be patient, as glow-worms often don’t show up until after 10pm in mid-summer. Artificial light confuses the males who mistake it for a possible female, heading for lamp-posts and security lights instead of potential mates.

On the bright side (no apology for the pun!), in recent years glow-worms have been spotted in churchyards, gardens, parks and campsites across the south. One farmer even reported seeing one on the back of a sheep and another behind a pig’s ear. There have been sightings in villages around Winchester, as well as St Catherine’s Hill, East Meon and the New Forest. Stockbridge Down, Burlesdon and Havant Thicket also seem to be regular haunts.

Whether this summer will be a success for the glow-worms remains to be seen, but given suitable, undisturbed habitat and a healthy diet of slugs and snails, we can be optimistic. They can be seen from late May to September, but are most visible in June and July. There is even a world Firefly Day on July 7, so I will be out with my torch checking the log-pile, in the hope of catching a glimpse of the luminous glow-worm.