Songs of love that only they can hear

Sanjida O'Connell finds many insects are on the same romantic wavelengt h

Summer holidays and exotic places conjure up the heavy hum of cicadas. But in fact many cicadas, crickets, grasshoppers and other insects sing silently. Airborne sound takes a lot of energy to produce; it requires transferring vibrational energy from a solid object to a gas at audible frequencies, and is an extremely inefficient process. For small insects, being quiet can be an advantage.

Singing is a way of attracting the opposite sex, but the problem is that eavesdroppers can tune in. Other males can lie in wait, then nip in and mate with the female you have spent hours serenading. It is also an auditory Belisha beacon for predators.

Silent singers make inaudible noises in three ways. Some fruit flies flick their wings to produce complex patterns of pulsed air that are decoded by their partners' antennae. The low frequency signals are in the 100-500Hz range. They are intense and highly directional, but travel for less than 10mm. Then there are the "tymbal singers", such as plant hoppers and spittlebugs. Males and females vibrate a pair of organs, the tymbals, located at the base of the abdomen. Energy is concentrated below 1kHz and transmitted to the ground via the legs or mouthparts. Green lacewings and tremulating katydids jerk or circle their abdomens at 30-120Hz, shaking the substrate at the same time. Sensitive receptors in their legs are tuned to the frequency range characteristic of their species.

One small fly uses this method to track down females. Virgin females hatch in widely scattered reed galls that they rarely leave. Moreover, the males do not fly; they walk. To avoid climbing every reed stem, the male remains at the bottom and vibrates it. He may have to do this for hundreds of stems for most of his life, but if he comes across a female, she will send a signal down the stem from her eyrie.

Because these silent songs are meant for one pair of ears only, they have become the exclusive province of insect romance. The privacy of virtual silence means the risk of detection by predators is low, and so courtship singing has evolved in females whowould otherwise be too sensible to broadcast their whereabouts. This has led to a decline in male fights and prolonged duetting between couples, rather than loud and indiscriminate advertising by males for any passing female.

Another effect is to increase the overall number of insect species. Usually, a new species will evolve if a genetic mutation accidentally confers some kind of benefit to the individuals within the species. Here new species arise in a completely arbitraryway by both males and females choosing each other on the basis of novel songs. Professor Charles Henry, of the Department of Ecology and Evolutionary Biology, University of Connecticut, says this could happen if songs were under relatively simple genetic control. A single mutation of the gene for singing could produce a new song "unacceptable'' to the rest of the species. He says "a single serendipitous success in mating by an individual bearing the mutation'' would be all it would take to introduce the new gene into the population. Unlike many of these so-called sibling species, the silent singers, who really differ only in their songs, can all coexist together. At least five species of lacewings have all been found in the same bush in North America.There were no hybrid species present and the lacewings flummoxed all attempts to create one in the lab.

Xie Ye, a Chinese poet whose work was recently read during the National Poetry Festival, takes poetic licence when she writes "insects make the earth sing''. Either that or she knew about the transmission of low frequency tremulation.

PROMOTED VIDEO
News
ebooksNow available in paperback
News
Valerie Trierweiler’s book paints Hollande as a cold-hearted hypocrite
people
Arts and Entertainment
Jennifer Lawrence as Katniss Everdeen in The Hunger Games: Mockingjay Part 1
filmsMockingjay Part 1 taking hit franchise to new levels
News
Bill Cosby
peopleActor has firmly defended himself against all claims
Life and Style
techSweet Peach says scent 'shows more important things are working'
Sport
Diego Costa, Ross Barkley, Arsene Wenger, Brendan Rodgers, Alan Pardew and Christian Eriksen
footballRodgers is right to be looking over his shoulder, while something must be done about diving
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Austen Lloyd: Clinical Negligence Solicitor

Highly Competitive Salary: Austen Lloyd: HAMPSHIRE MARKET TOWN - A highly attr...

Ashdown Group: IT Systems Analyst / Application Support Engineer (ERP / SSRS)

£23000 - £30000 per annum + pension, 25days holiday: Ashdown Group: An industr...

Ashdown Group: Junior Reports Developer / Application Support Engineer

£23000 - £30000 per annum + pension, 25days holiday: Ashdown Group: An industr...

Recruitment Genius: Client Support Officer

£10 - £11 per hour: Recruitment Genius: The candidate must be committed, engag...

Day In a Page

In a world of Saudi bullying, right-wing Israeli ministers and the twilight of Obama, Iran is looking like a possible policeman of the Gulf

Iran is shifting from pariah to possible future policeman of the Gulf

Robert Fisk on our crisis with Iran
The young are the new poor: A third of young people pushed into poverty

The young are the new poor

Sharp increase in the number of under-25s living in poverty
Greens on the march: ‘We could be on the edge of something very big’

Greens on the march

‘We could be on the edge of something very big’
Revealed: the case against Bill Cosby - through the stories of his accusers

Revealed: the case against Bill Cosby

Through the stories of his accusers
Why are words like 'mongol' and 'mongoloid' still bandied about as insults?

The Meaning of Mongol

Why are the words 'mongol' and 'mongoloid' still bandied about as insults?
Mau Mau uprising: Kenyans still waiting for justice join class action over Britain's role in the emergency

Kenyans still waiting for justice over Mau Mau uprising

Thousands join class action over Britain's role in the emergency
Isis in Iraq: The trauma of the last six months has overwhelmed the remaining Christians in the country

The last Christians in Iraq

After 2,000 years, a community will try anything – including pretending to convert to Islam – to avoid losing everything, says Patrick Cockburn
Black Friday: Helpful discounts for Christmas shoppers, or cynical marketing by desperate retailers?

Helpful discounts for Christmas shoppers, or cynical marketing by desperate retailers?

Britain braced for Black Friday
Bill Cosby's persona goes from America's dad to date-rape drugs

From America's dad to date-rape drugs

Stories of Bill Cosby's alleged sexual assaults may have circulated widely in Hollywood, but they came as a shock to fans, says Rupert Cornwell
Clare Balding: 'Women's sport is kicking off at last'

Clare Balding: 'Women's sport is kicking off at last'

As fans flock to see England women's Wembley debut against Germany, the TV presenter on an exciting 'sea change'
Oh come, all ye multi-faithful: The Christmas jumper is in fashion, but should you wear your religion on your sleeve?

Oh come, all ye multi-faithful

The Christmas jumper is in fashion, but should you wear your religion on your sleeve?
Dr Charles Heatley: The GP off to do battle in the war against Ebola

The GP off to do battle in the war against Ebola

Dr Charles Heatley on joining the NHS volunteers' team bound for Sierra Leone
Flogging vlogging: First video bloggers conquered YouTube. Now they want us to buy their books

Flogging vlogging

First video bloggers conquered YouTube. Now they want us to buy their books
Saturday Night Live vs The Daily Show: US channels wage comedy star wars

Saturday Night Live vs The Daily Show

US channels wage comedy star wars
When is a wine made in Piedmont not a Piemonte wine? When EU rules make Italian vineyards invisible

When is a wine made in Piedmont not a Piemonte wine?

When EU rules make Italian vineyards invisible