Japanese poets compose haiku about them, children keep them as pets and they were once believed to be the souls of dead kamikaze pilots. Now Japan's beloved fireflies, the tiny insects whose flickering light is a symbol of the transience of life, are under threat - not from birds or insecticide, but from human poachers.

Firefly rustlers have been snatching the creatures from a famous insect-viewing ground in Fussa, west of Tokyo. The creatures, whose numbers have declined over the years because of pollution and creeping urbanisation, are sought by dealers who sell them to hotels and restaurants for summer firefly displays.

Warning signs denouncing insect thieves have been erected and teams of volunteers have been mounting nightly patrols to ward them away from Fussa's Firefly Park, where tens of thousands of people converge every summer for the firefly festival.

In one night alone, 80 per cent of the resident fireflies disappeared after a section of fence was removed from the protective dome where the insects are raised. A display of 250 fireflies was reduced to 50 the following evening, prompting the local police to threaten criminal charges against anyone caught red-handed.

The earliest records of firefly watching date back to Japan's Heian Period in the 9th century, and since then they have been a much loved ingredient of the long hot Japanese summer. Thirty species of firefly are found in the country, but the most sought after is the Genji Firefly or Luciola cruciata.

The larvae breed in water and the mature insects can be seen along river banks on summer evenings, signalling to potential mates with flickering luminescence in their tails. The light, which is pale red, green or yellow, is caused by an enzyme called luciferase.

The flies spend nine months as larvae but survive for barely a fortnight. The brevity of their existence has made them a symbol of the transience and poignancy of life. In the past they were taken to be the souls of the dead, and in 1945 they were identified with kamikaze pilots who were being sent to their deaths at the end of the Second World War.

People who lived close to the airbases from which the pilots flew reported seeing new lights blinking after a unit of planes had departed on a kamikaze mission.

Collecting insects is one of the traditional summer pastimes for Japanese children, but the scale of the losses at Fussa suggests an organised commercial smuggling operation. Although pollution of lakes and streams has caused the firefly population to shrink, there has been a consistent demand for the insects from restaurants and hotels which offer firefly-viewing menus during the summer months.

A mature firefly sells on the internet for 300 yen (£1.40) and larvae, or glow worms, can fetch as much as 400 yen. This is believed to have motivated the thefts.

Last year environmentalists in Turkey gave warning that a species of local stag beetle was being pushed towards extinction because of a craze among collectors in Japan.

On and off the trail

— Fireflies are not flies, but beetles of the Lampyridae family.

— Most firefly larvae are found in rotting wood or forest litter on the edges of streams and ponds. Some Asian species have tracheal gills and live underwater.

— The greatest numbers of firefly species are found in tropical Asia and Central and South America.

— Firefly larvae feed on eathworms, snails and slugs. They can detect snail trails, follow them to their prey and then inject it with an anesthetic.

— Fireflies produce light through a chemical reaction between luciferin, luciferase and oxygen.

— There are several competing theories to explain how they turn their light on and off. One is that the mechanism is triggered by controlling the oxygen supply to the photic organ

Source: Ohio State University

Times recommends

• Prince Philip attacks big families
• Take a dip in Dubai-on-Thames
• Eco Worrier: How can I persuade my husband to use a push mower?