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There are 120,000 described species of aquatic moths found worldwide.
  • In North America, there are 11,000 different species within 75 families.
Most aquatic moths are herbivores. 
  • Some species eat plant foliage, while others eat (and burrow into) into stems or roots of plants.
  • These larvae also feed on algae and diatoms found on rock surfaces.
  • As adults, aquatic moths primarily feed on flower nectar making them important pollinators.
  • Sometimes, however, adults may not feed at all due to short life spans.
  Aquatic moth          
                                                                                              Source: Murray Darling Freshwater Research Centre
Aquatic moth larvae can be found in still, slow, or rapidly flowing water-bodies that are unimpaired.
  • They tend to live along the river substrate (meaning that they are 'benthic') on rocks or among vegetation.
  • Larvae can build shelters using silk thread that is produced by special glands.
  • The silk is used to bind leaves into portable cases, which are used to for protection to hide from predators.
  • Larvae can also find shelter from predators by burrowing into the stems of aquatic plants; they chew out a hole, consuming the vegetation and hiding in the hole created.

Aquatic moths undergo 'complete metamorphosis', which involves passing through four complete life stages. These are the egg, the larvae, the pupa, and the adult stages. 

  • Adult females usually deposit their eggs on rocks under the water at night.
  • Some pond-dwelling species may attach their eggs to the underside of leaves that are hanging over the surface of the water.
  • It takes approximately six days to two weeks for the eggs to hatch, unless they are laid in the fall.
  • In cases where the eggs were deposited in the fall, they will overwinter as eggs.
  • Larvae may go through anywhere from five to seven stages of development, called 'instars', depending on the species.
  • The life span of the larval stage varies depending on environmental conditions, and some may overwinter as larvae.
  • When the larva is fully developed and ready to pupate, it creates a cocoon using silk and leaves in the water.
  • When it has transformed into its adult stage, the pupa will chew a tiny slit along one side of the cocoon in order to emerge.
  • The pupal stage generally lasts less than one month.
  • After emerging from the cocoon, the adults swim to the water's edge and drag themselves out of the water.
  • They must find shelter in a safe and dry place in order to wait for their wings to dry.They are then able to take flight.
  • The adult life span can range from one day to two months, depending on the species and the environmental conditions.
  • Although they are terrestrial, adult aquatic moths will stay close to aquatic habitats.
  • The entire life span of an aquatic moth is usually approximately one year, and they overwinter either as larvae or pupae, but rarely as eggs or adults.
  • The scientific name, of the aquatic moth, which is 'Lepidoptera', comes from the Greek words Lipdo=scale and ptera=wings. The name refers to the scales that cover the body and wings of most adults.
  • To identify a caterpillar or moth as aquatic and not terrestrial, you can check for filamentous gills on the body. Another difference is that the aquatic forms may have a portable case.
  • Butterflies tend to fly during the daytime, while moths usually fly during the night.
  • Larvae living in different habitats have different ways of breathing. Those that live in slow flowing water may not have breathing gills, while those that live in fast flowing waters require gills in order to breathe.

Brusca, R. C, and Brusca, G. J., 2003. Invertebrates, 2nd ed. Sinauer Associates, Inc., Publishers, Massachusetts. Page 600.
Canada's Aquatic Environments (2002). Lepidoptera. Available here.
Murray Darling Freshwater Research Centre (2006). Lepidoptera (aquatic caterpillars) Crambidae. Available here.
North Carolina State University, Department of Entomology (2005).Lepidoptera. Available here.
University of Minnesota (2010). Class Insecta, Order Lepidoptera: Butterflies and moths. Available here.
Univeristy of Minnesota; Guide to Aquatic Invertebrates of the Upper Midwest (2004). Lepidoptera. Available here.
Virgina Polytechnic Institute and State University, Department of Entomology (1996). Lepidoptera (Moths, Butterflies, and Skippers). Available here.