A tiny insect that plays love songs with its penis is the loudest animal on Earth.
Scientists from France and Scotland recorded the aquatic animal "singing" at up to 99.2 decibels, the equivalent of listening to a loud orchestra play while sitting in the front row.
The two-millimetre insect creates the sound by rubbing its penis against its abdomen in a process known as "stridulation" - making it the noisiest species relative to its size.
Researchers say the song is a courtship display performed to attract a mate.
Micronecta scholtzi are freshwater insects measuring just 2mm that are common across Europe.
In a study published in the journal PLoS One, the scientists discovered that the small animals were making the sound, which was recorded using underwater microphones, researchers from University of Strathclyde in Glasgow said.
Dr James Windmill told the BBC: "It's so loud; a person walking along the bank can hear these tiny creatures singing from the river bottom.
"If you scale the sound against their body size, they are the loudest on Earth."
On average, the songs of M. scholtzi reached 78.9 decibels, comparable to a passing freight train.
"We were very surprised. We first thought that the sound was coming from larger aquatic species such as a Sigara species [of] lesser water boatmen," said engineering expert Dr James Windmill from the University of Strathclyde, Glasgow.
"When we identified without any doubt the sound source, we spent a lot of time making absolutely sure that our recordings of the sounds were calibrated correctly."
Dr Windmill explained that the reason the insects don't deafen us is down to the bug's underwater lifestyle.
Although 99% of the sound is lost when transferring from water to air, the songs were still loud enough to be audible to the human ear.
"The song is so loud that a person walking along the bank can actually hear these tiny creatures singing from the bottom of the river," said Dr Windmill.
The majority of the loudest animals on Earth are also the biggest, with blue whale songs reaching 188 dB and elephants' rumbling calls measuring 117 dB.
"If you scale the sound level they produce against their body size, Micronecta scholtzi are the loudest animals on Earth," said Dr Windmill.
Explaining why the insects were "singing", biologist and co-author Dr Jerome Sueur from the Museum of Natural History, Paris, told the BBC:
"We assume that this could be the result of a runaway selection," biologist and co-author Dr Jerome Sueur from the Museum of Natural History, Paris, told the BBC.
"Males try to compete to have access to females and then try to produce a song as loud as possible potentially scrambling the song of competitors."