Dragonfly larvae, also known as nymphs, are the aquatic immature stage of dragonflies. These fascinating creatures spend the majority of their lives underwater, often for several months or even years, before transforming into the familiar winged adults. They are formidable predators within their freshwater habitats, playing a significant role in their ecosystems. These nymphs are an integral part of the dragonfly life cycle, which involves incomplete metamorphosis with three stages: egg, nymph, and adult.
General Appearance
Dragonfly larvae exhibit a robust and often stout body shape, varying in size from about 0.25 inches to 2.5 inches in length depending on the species and age. They typically possess six jointed legs, positioned on a segmented body that includes a head, thorax, and abdomen.
Their coloration usually consists of drab browns, greens, or grays, providing effective camouflage against the sediment, submerged plants, or debris in their aquatic environments. This muted coloring helps them blend in with their surroundings, allowing them to ambush unsuspecting prey or hide from larger predators like fish and waterfowl. Some species may even have hairs that collect silt or organic debris, further enhancing their camouflage.
Key Identifying Features
A distinguishing feature of dragonfly larvae is their specialized mouthpart called the labium, often referred to as a “mask.” This hinged, scoop-like lower jaw is disproportionately large and folds beneath the head and thorax when not in use. The labium can extend rapidly, in milliseconds, to seize prey with its fang-like pincers.
Dragonfly nymphs also have large, prominent compound eyes located on the sides of their heads, which are well-suited for detecting movement in their aquatic environment. Their six legs are strong and often spiny, adapted for grasping onto submerged vegetation or substrate and for crawling. Small wing buds are visible on the back of their thorax, which will develop into wings as they mature.
Unlike damselfly larvae, dragonfly larvae lack external gills at the end of their abdomen. Instead, their gills are internal, located within the rectum. They breathe by drawing water into and expelling it from their hind end. This unique respiratory mechanism also allows them to move quickly through the water using a form of jet propulsion.
Distinguishing from Similar Aquatic Insects
Differentiating dragonfly larvae from other aquatic insects requires careful observation of their specific physical characteristics. Damselfly larvae, for instance, are generally more slender and elongated compared to the typically broader and flatter bodies of dragonfly larvae. A primary distinction lies at the end of their abdomen: damselfly larvae possess three distinct, leaf-like external caudal gills, which function for both respiration and propulsion.
Mayfly nymphs are another common aquatic insect that can be mistaken for dragonfly larvae. Mayfly nymphs typically have plate-like gills positioned along the sides of their abdomen, a feature absent in both dragonfly and damselfly larvae. They also often have two or three long, thread-like tails extending from the end of their abdomen, which are different in structure from the caudal lamellae of damselflies. These clear visual differences in gill location and tail structure are important for accurate identification.