Living in the sediments at the bottom of ponds and rivers larvae are voracious eaters, and a late stadium dragonfly larva may tackle prey as large as a Stickleback. Most are ambush hunters, using camouflage colouring they hide very still and capture prey as it passes close by unawares, but some species actively stalk prey. Either strategy can utilise visual or tactile methods of finding their food. Species that inhabit clear running water favouring visual strategies, and in murky waters the bottom dwelling species relying more on tactile strategies.
Uniquely amongst insects, Odonata larvae have specialised mouth parts called the labium or mask, that can be extended at great speed and is used like a pair of pincers, grasping its prey. The time taken to extend the mask is very rapid, in the order of 15-40 milliseconds; victims are caught literally before they know what’s hit them. Once captured, the larvae devour its prey using powerful mandibles that can easily deal with the flesh of fish and tough cuticles of insects.
As adults, dragonflies and damselflies are accomplished flyers and hunt other insects on the wing – they are exclusively carnivorous and do not eat vegetation.
With excellent almost 360° vision keyed on movement, and the ability to hover, fly forward, sideways, and backwards, Odonata can capture prey easily. Dragonflies will take prey as large as damselflies and butterflies, and sometimes smaller dragonflies too. Damselflies usually concentrate on small flies and similarly sized prey but occasionally they too will prey on other damselflies.
Generally, Odonata capture prey by extending their legs in flight and using them as a kind of net or basket. Larger dragonflies such as Hawkers will capture and eat prey on the wing, but other smaller species will often perch on a branch or reed and launch an attack on something that catches its eye, often flying back to the same perch to feed. Unlike some insects, Odonata do not sting their prey, nor do they digest food outside their body; they eat their victims using powerful mandibles with tooth like serrations. Odonata means ‘toothed one’.
Whilst generally towards the top of the insect food chain, adult and larval Odonata do have predators. Dragonflies are agile and able to avoid predation by most birds, but raptors will take them. Damselflies being weaker and slower fliers offer an easier meal. Damselflies in particular are often caught in spiders’ webs. Other insects like Hornets are able to kill a dragonfly and will make short work of one.
A particularly dangerous time for Odonata is emergence, where they can neither return to the water or fly, Dragonflies often emerge at night, presumably in an effort to avoid daytime predation by birds. Another technique used by some species is synchronised emergence, where large numbers emerge together – effectively swamping a predator’s ability to focus on a single insect, this helps cut down on the likelihood of an individual being eaten.
Odonata are also vulnerable to parasites; it’s not uncommon to see damselflies with external mite infestations, and larva and adults are hosts to many internal parasites.