BugFest: Five fascinating facts about dragonflies, fierce, territorial predators

The N.C. Museum of Natural Sciences' BugFest is Saturday. The free festival, now in its 21st year, draws tens of thousands to the downtown Raleigh museum for games, crafts, demonstrations, presentations and even a Cafe Insecta where insects are the main ingredient.

Many people don’t know that dragonflies start off their lives underwater! Most dragonfly species lay their eggs in either ponds or streams and the juvenile dragonflies (the nymphs) that hatch from them will live in the water until they become adults.

Many people are familiar with the butterfly life cycle: egg, larva, pupa, and adult. The dragonfly life cycle is simpler, with an egg, nymph, and adult. While dragonfly nymphs don’t look exactly like the adults, they look a lot more like the adults than a caterpillar looks like a butterfly! This is because dragonflies don’t completely change form the way caterpillars do and instead go straight from a non-winged nymph to a winged adult.

Adult dragonflies live outside of the water, so they undergo what’s called an emergence when they transform from a nymph to an adult. The nymph typically crawls out of the water and up the stem of a plant. It puffs its body up (often by swallowing air and pumping blood into specific parts of its body) and cracks the exoskeleton open. The adult then pulls itself out of the exoskeleton and expands its wings and adult body. Once everything is fully expanded, the new exoskeleton hardens and the adult dragonfly can fly away.

Dragonfly females choose their mates based on where they want to lay their eggs — they mate with the male they find at their chosen site. As a result, there is fierce competition between male dragonflies of the same species to control the most desirable places. Male dragonflies divide a pond or stream into territories of various qualities and the strongest, best males get the best territories along with the most mates. The weaker males take the lesser territories where fewer females are interested in laying their eggs, while the weakest males might not get to fly near the water at all! A dragonfly moves into a better territory by fighting (and beating!) the male that holds it.

Dragonflies are predators as nymphs and adults. They are often among the top predators in ponds and streams and eat other insects (including other dragonflies!), small fish, small tadpoles or frogs, and other animals. Dragonfly nymphs have a unique, long hinged mouthpart that helps them hunt, that they grab and hold their food with while they chew it up. Adult dragonflies also eat other animals, including mosquitoes, other flies, butterflies, and other dragonflies and use their long legs to help them catch food as they fly. Some species of dragonflies have been known to catch and eat hummingbirds! Dragonflies are an important balancing force in nature and help prevent prey populations from getting too big throughout their lives.