Insects That Hatch in Water

Updated July 20, 2017

Fly-fishermen know the emergence of aquatic insects from water as the "hatch." Fish feed on these insects, which range in colour, size and species. The great challenge for fly-anglers is to "match the hatch"; this involves selecting artificial flies that closely replicate the real species of insects hatching. If anglers are able to "match the hatch," they have a better chance to catch more fish. Fly-fishermen need to understand the life cycle, appearance, habitat and other unique traits of all the different types of flies that trout like to eat: mayflies, stoneflies, caddisflies and many others.


Mayflies, also known as dayflies, shadflies, lake flies, fish flies, and jinx flies, are aquatic insects belonging to the order Ephemeroptera. Interestingly enough, these aquatic insects spend a longer time in the immature stage (spent in freshwater) than in the adult stage. This stage will span anywhere from between a few minutes to one day, depending on the species. The eggs are deposited in lakes or streams, which then sink to the bottom. As such, the naiads (the term used for the immature mayflies) may spend their first few years under rocks or in the sediment. As adults, they are known for their short antennae, large compound eyes (particularly the males), and membranous wings. Mayflies are one of the few insects (if not the only) that possess paired genitalia, with each of the aquatic insects possessing two organs of their gender.


Caddisflies are aquatic insects that belong to the order Trichoptera. Experts believe that these are usually found in clean waters, including streams, lakes, rivers, ponds and vernal pools. Caddisflies closely resemble moths in appearance. Several of the species belonging to the order Trichoptera spin silk mixed with gravel, sand or other debris found in the area where they live as a protective net. These cases greatly resemble the nets of bagworms but are usually open on both ends. Depending on the species, a caddisfly may build the net as larvae until they are ready to pupate.


Stoneflies are aquatic insects belonging to the order Plecoptera. According to the website Kendall UK, stoneflies are one of the most ancient breeds of insects, with some stonefly fossils found dating back to the Carboniferous geological period. The modern stonefly emerged during the age of dinosaurs (Mesozoic period). The presence of stoneflies along with mayflies and caddisflies is a good indication that the water source has good quality, according to the website King County Government. While most stoneflies have wings that lie flat on their backs, some species are wingless, as they are aquatic from birth to death.


Midges are like caddisflies as they exhibit a complete metamorphosis, from a larva, pupa, and adult stage. The caddisflies larvae live within stagnant pools, predominantly within water where there are many aquatic weeds. In slow, steady waters like creeks, small streams and some rivers, midges will make up most of the insect food supply for small fish, such as trout that live within waterways.

Spring Flies

During early spring, all it takes is a little sunshine for a "big hatch" to occur. With warmer temperatures, adult flies use this time to give birth to their offspring. Fly-fishermen will notice trout rising to snatch flies that land upon the water. To help in selecting the correct artificial fly to use, try to match the colour and size of the flies that land on the water during a hatch. According to Orvis website, dry flies such as adams parachute, nymphs like the bead-head pheasant tail and the woolly-bugger streamer are top spring baits to catch "game fish."

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About the Author

Thomas Ganio began writing in 2006 for the "Northern Virginia Daily," a community newspaper in Richmond, Va. As a freelance writer, he has also contributed to "The Maryland Springs Gazette" and the Parks and Recreation Department of Richmond County, Md. Ganio holds a Bachelor of Arts in social science and English from James Madison University.