Dragonflies and aquatic insects

Did you know that dragonflies are carnivorous? Baby dragonflies (dragonfly larvae)
use their fast, extendable jaws to catch unsuspecting prey. They eat tadpoles,
fish, and other waterbugs – including each other!



Adult dragonflies always catch their prey mid-flight. They hunt small insects
including midges, flies, and mosquitoes. An adult dragonfly can eat up to hundreds
of mosquitoes per day, making dragonflies very important for their population control.

Dragonflies get eaten by spiders, fish, frogs, birds – and even by other dragonflies
that are bigger than them!


Adult dragonfly wings work independently of each other, which makes dragonflies very
acrobatic flyers. They can move straight up and down, hover, pivot on the spot,
and even suddenly switch to flying backwards! Dragonflies are also very fast, reaching
speeds of up to 40km/h.
Dragonflies have existed for over 300 million years. Fossil records show that in
prehistoric times that they used to have a wingspan of up to 80cm!


Dragonflies start their life as larvae living in water and breathe using gills. Some
dragonflies stay as larvae for up to 2 years. At the end of their larval stage they
crawl out of the water, which initiates their lungs to start breathing from air. Their
exoskeleton cracks open from the back of their skull and the adult dragonfly
emerges – its abdomen pops out like a folded accordion and its wings slowly uncurl
and harden in the sun. Adult dragonflies may only survive for a few months, or up to a year.

Dragonflies are one of many types of aquatic insects that spend part or all of their
lives in water. These waterbugs are an important food source for living things like fish and
frogs. Although dragonflies are predators many waterbugs are shredders, collectors,
filter feeders, or scrapers, meaning they feed on organic matter such as leaves, woody
debris, and algae. So they are also important for keeping our waterways clean by helping to
decompose organic matter and break down nutrients.

We can also play a part in keeping our waterways clean so that dragonflies and many
other beautiful aquatic insects can survive to adulthood. Maintaining vegetation in
and around a creek is the most important thing we can do. Plants growing in the water
like rushes and sedges provide habitat for waterbugs. Trees and shrubs growing on banks
also provide habitat via the logs, bark and leaves that fall in the water. Leaf litter is also
an important food source for a large portion of water bugs. All of these plants also help
reduce erosion of banks, slow water flow during floods, provide a mix of bright and dark
areas in the waterbody, and regluate water temperature by providing shade.


Many species of dragonfly larvae require pristine water quality to live in, including high
oxygen levels and very specific water temperatures. Their presence often indicates clean
water quality. Living things that can indicate the health of an ecosystem are called
“bioindicators”.

Most waterbugs are bioindicators. By doing a survey of what’s living in the water, we can find
out the health of the water. If the only species present are ones that can survive in polluted
waters, then we know that the ecosystem is not healthy. However if there is a good variety
of species including ones that can only live in clean water, then we know that the
ecosystem is healthy.


Please contact our ECO Education Service team to request a waterbug
survey workshop or fieldtrip.



This post was made possible by grant funding received from the Australian Government through the National Landcare Program.