The glow worm is a small beetle, up to 1cm in length, with a sexually dimorphic lifestyle. Female glow worms are flightless and able to “glow” producing a bright green light which is attractive to the winged males who use their ability to fly to search out receptive females.

Glow worms preferentially occupy areas of unimproved chalky or limestone grassland but will use areas of grazed grassland, gravel and hedgerows where the larval stages feed on a wide variety of snails. Glow worms normally take three years to develop to adult status. The females glow until they mate and die soon after laying their eggs.

Glow worm populations are concentrated in the south of England but isolated populations have been recorded throughout much of England, Scotland and Wales.

The glow worm is nationally scarce particularly in the north of England and most of Scotland. Numbers of glow worms are suspected to be declining throughout their range but no single cause has been identified. Records of this beetle since 1980 are approximately half of the number found earlier in the 20th century.

The flightless nature of the females means that the species has difficulties in colonising new sites and is vulnerable to local extinctions.

The glow worm is believed to be declining in the Durham area.

There is no complete survey information for glow worms in the Durham area.

The largest glow worm population in Durham is at Thrislington Grassland NNR, where numbers have declined dramatically over recent years.

Lack of detailed knowledge on the habitat requirements of this species.

Loss of suitably grazed grassland – glow worms are thought to be vulnerable to both overgrazing and undergrazing including loss of available food supply in areas of overgrazed grasslands where mollusc numbers are low.

Use of molluscicides.

Fragmentation and loss of habitat – glow worms have difficulties in colonising new habitats.

Light pollution – overhead lights may deflect males from glowing females.

Disturbance and collection of glowing females.

Protection of key sites for the species.

Provision of advice on appropriate management of grasslands for invertebrates.

Raised awareness of the species and its habitat requirements.

The glow worm is not protected.