The public are being urged to help find a rare insect which has not been spotted in Hampshire for 20 years.
The mating call of the New Forest cicada is so high-pitched children and adults under the age of 40 have a better chance of hearing it.
University of Southampton has developed free software for smartphones to detect the insect's call.
An organised hunt by the New Forest National Park Authority takes place from 7-8 June.
The New Forest cicada, which is about 4cm-long (1.5in), is the the UK's only native cicada.
Scientists at University of Southampton described it as "very rare" and said although sightings of the insect within the park date back to 1812, the last confirmed sighting was in 1993.
Its mating song, which experts describe as a "constant hiss", can be heard between May and July.
The pitch falls between 14-15kHZ and an adult human's hearing range is about 20Hz to 20kHz, but "greatly reduces" with age.
Dr Alex Rogers, from the university's faculty of physical sciences and engineering, said: "Modern smartphones have extremely sensitive microphones and enough computing power to automatically detect and recognise the song of the New Forest cicada.
'We're hoping that the millions of visitors to the New Forest National Park can use their smartphones to help us locate any remaining colonies of the cicada that might remain in the forest."
The New Forest National Park Authority's BioBlitz event, which will include a hunt for the cicada, charts all species sightings including insects, birds, bats and moths over a 24-hour period.
It will be held at Roydon Woods Nature Reserve near Brockenhurst from 7 June.
The Cicada Hunt app is available from 3 June.