Glow worm

Glow worm by John TylerGlow worm by John Tyler

Lampyris noctiluca

The common glow worm is not at all worm-like but is a beetle up to 25mm long. Only the wingless females glow strongly, to attract the flying males. Each individual female has an adult glowing life of only a few weeks - once a female has mated, she turns off her light, lays her eggs and dies. Adult glow worms do not feed so they only live for 14 days or so. 

In Britain, the glow-worm is fairly widespread, but local in distribution. The beetles are usually found on grassy slopes, verges and hedgebanks, on heaths and in open grassland, especially in chalky and limestone areas. People are often surprised to discover glow worms in gardens, or along footpaths and railway embankments. They are rarely found on cultivated agricultural land.

The glow worm needs a comparatively open area where the females can display to attract a male in June, July and August. Glow worm larvae need a supply of small snails and slugs to feed on and patches of vegetation where they can find the snails. They paralyse them before sucking them dry. They remain as larvae for one or two further summers which explains the two or even three-year gap between a mating and the subsequent appearance of adults.

Light pollution has increased enormously and there is no doubt that male glow worms are attracted to artificial lighting and this must distract them from finding females. But without a detailed long-term site survey with accurate and consistent before-and-after results there is no firm evidence that this does cause a decline. However, as most glow worm sites are in dark areas, this suggests that lights do cause a decline. Other causes of decline are changes in habitat such as development, use of pesticides and changes in land use such as cessation of grazing.

Many of our reserves provide the right habitat conditions for glow worms. They are present on Blaxhall Common, Carlton & Oulton Marshes, Redgrave and Lopham Fen, Roydon Fen and Newbourne Springs.

Glow worms are one of many species benefiting from the large-scale heathland restoration undertaken by the Trust over the past 25 years. Open areas are created by clearing trees and scrub and maintained by pony and sheep grazing. The Sandlings Living Landscape vision aims to increase the amount of heathland within the Sandlings and link heathland areas creating more habitat for species like glow worms.

For further information about glow worms and to record your sightings visit the UK Glow Worm Survey website.