Crambidae (formerly part of the Pyralidae)
Most folks do not realise that there are moths that have an aquatic existence during their life cycle. This is usually during the larval (caterpillar) stage. These moths can be very abundant at times as illustrated by their appearance at lights. They can also cause destruction to aquatic plants, especially water lilies, by chewing the leaves and folding them over to conceal the caterpillars and cocoons. If you have a pond, you probably have some of these moths around. And you are probably distressed over their feeding activities because they can reduce water lily leaves to shredded, unattractive bits and pieces (Have a look at the examples on the website). And you can’t really spray them because it would affect the aquatic life in the pond. Still there are other larvae that live on rocks in the water and feed on plankton. Many have gills to supply oxygen; others have a plastron or can respire subcutaneously.
Aquatic crambids are members of a subfamily, the Nymphulinae. The attractive moths are nocturnal and deposit their eggs in the aquatic habitat. They have a rather complex life history in aquatic vegetation. The cocoon consists of leaf pieces to enclose the pupa. This stage can last for up to a month. The cocoon may be below the water surface requiring the emerging adult moth to swim or drag itself to the surface. Adults live form one day to a couple of months.
The Australian aquatic moths are under study and the identifications below are tentative.Tetrernia terminitis Meyrick; Acentropinae
Theila siennata (Warren); Acentropinae
Talanga tolumnalis (Walker); Pyrautinae
Margarosticha euprepialis Hampson: Acentropinae
Araeomorpha limnophila (Turner): Acentropinae