Sarah Ladbrook, of Balclutha School, asks :-

Why do some worms glow?

Fiona Gordon, of Otago University's Department of Human Nutrition, responded.

Perhaps the name glow worms is a mis-noma as they are predatory lavae not really worms.

The glow worm is the immature stage (larva) of a mosquito-like fly. The adults are short-lived and do not feed. Glow worms are found under overhangs and in caves. They construct snares made of mucous-coated silk threads. During the day they retreat into crevices. At night they produce a bioluminescent glow from their posterior end. Small flying insects are attracted to the glow and trapped in the sticky snare. The larva then consumes them.

The blue glow of the larvae is the result of a reaction between body products and oxygen in the enlarged tips of the lavae's excretory tubes. The light is the result of a chemical reaction involving several components: luciferin ( a waste product ), luciferase ( the enzyme that acts upon luciferin ), adenosine triphosphate ( the energy molecule ), and oxygen.

All these combined make an electronically excited product capable of emitting a blue-green light. To the average person's sight the light appears more blue than green , but spectrometer readings show the colour is actually green.

Direct moonlight affects viewing of glow worms in exposed area colonies. Only the brightest worms in exposed colonies are visible on full moon nights.