Micronecta scholtzi, also known as the lesser water boatman, is a species of water boatman in the family Corixidae in the order Hemiptera. They are some 2 mm long and are common in freshwater ponds and lakes across Europe, preferring stagnant to moving water. It is one of some 45 species of Hemiptera used to assess and monitor the health of freshwater bodies. The genus Micronecta is represented by five species, of which four are to be found only in permanent fresh water lakes.A team of biologists and sound engineers from France and Scotland have recorded M. scholtzi producing sound up to 99.2 decibels, a volume comparable to a passing freight train.
The male of this species produces its underwater courtship song by stridulating a ridge on its penis across corrugations on its abdomen, the area involved measuring only 50 micrometres across, or about the thickness of a human hair. Almost all volume is lost when sound moves from water to air, but even so remains audible to humans walking along the pond shore. For its size this species is considered the loudest of all animals.