Common Glow-worm

Fast Facts

Latin name: Lampyris noctiluca

Notable feature: Females emit a yellow-green glow at night, making them unmistakable for any other beetle

Conservation Status: Not Evaluated

Where in the UK: The Common Glow-worm, as its name suggests, is common across Britain, but is not present in Northern Ireland. Usually found in long-established grassland, typically on calcareous substrates, which may include meadows, railway embankments, road verges and woodland edges; more common in the south of England and Wales but also found in lowland Scotland.

Common Glow-worm (Lampyris noctiluca) © Pchelovek1205 (CC BY-SA 4.0 Wikimedia Commons)

The Common Glow-worm (Lampyris noctiluca) despite its name is not a worm, but a beetle; belonging to the family Lampyridae, commonly known as fireflies.  It is one of two glow-worms found in the UK and is a native, medium-sized, narrow beetle.  Also known as Firefly, Common European Glow-worm and European Glow-worm, this beetle is locally common in England and Wales, becoming more scattered and scarce to the far north of Scotland and absent from Northern Ireland.

The male Common Glow-worm looks like an ordinary beetle with hard wing cases and can fly (although they are not strong fliers); the flightless female is larger than the male, is dark in colour with a thin pale line down the centre of its body, she has flattened body sections and no wings at all.

Only the adult female glows brightly, caused by a chemical reaction in the final two segments of their abdomen creating a bright greenish-yellow glow (bioluminescence).   They can glow for several hours at a time as soon as it gets dark, with the glow being used to attract a mate; they switch off their glow once they have mated.  The adult female tends to live a short, sedentary life, rarely moving more than 30cm from one night to the next.

Common Glow-worm larvae look very much like the wingless females but have pale spots at the rear edge of each segment.  The larvae can produce a weak intermittent light that is easily overlooked.

    • Size: Females measure between 15-25mm in length. Males measure 15-18mm in length. Larva measure 3-25mm in length
    • Life span: Larvae develop for around 3 years, before pupating for between 10-15 days to then emerge as adults.  Adult Glow-worms can’t feed and as a result only live for between 14-21 days.
    • Diet: Common Glow-worm larvae eat small slugs and snails which they apparently paralyse before sucking them out of their shells.  Adult Common Glow-worms lack functional mouth parts and therefore cannot eat.
    • Reproduction: The female Common Glow-worm lays between 50-200 eggs in the ground; in leaf litter, moss or soil over a three day period,  dying shortly afterwards.  After 2-3 weeks the eggs hatch and they remain as larvae for around 3 years before fully maturing.
    • When to see:  Active from May to September, with peak activity during June and July.  Easiest to see at night when their glow is more obvious.
    • Population Trend:  Declining.  Studies have shown that glowing females are declining with some studies suggesting declines of 75% over 18 years in England.  Populations in Scotland are fragmented and under recorded as are populations across Europe
    • Threats:  The Common Glow-worm is a species that shares threats with many other invertebrates, such as habitat loss and fragmentation (resulting in isolation and unsustainable subpopulations), pesticide use, climate change and changes in weather patterns.  The Common Glow-worm is directly impacted by light pollution due to their reliance on light-based signals for mating.
    • Fun Fact:  There are over 2,000 lampyrid species globally yet only two are currently found in the UK.  Adult Common Glow-worms burrow under the soil during the day to avoid predators, then emerge at night to put on a light show.

How you can help: 

Buglife is working to increase awareness of invertebrates and the Common Glow-worm through specific projects and campaigns such as our Light Pollution campaign “Nurture the Night Shift” and Species Champions.

Join a recording scheme and log your finds – send any records/sightings to Glow-worms UK or download the iRecord app and get recording!

Stephen Kerr MSP – Common Glow-worm Nature Champion

Common Glow-worm Nature Champion:

Stephen Kerr MSP

  • Member for: Central Scotland
  • Region: Central Scotland
  • Party: Scottish Conservative & Unionist Party

Find out more about Scottish Nature Champions

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