Wednesday, July 24, 2024

An eastern forktail damselfly, so named because the males have tiny projections off the end of their body. (Photo: Tom Murray)

Damselflies, also called darning needles, mosquito hawks or even neon toothpicks, are colorful predatory flying insects with slender bodies, large eyes and clear wings. They are similar to dragonflies but smaller and slimmer. They fold their wings along their body – unlike dragonflies, which hold their wings out from the body.

Fossil records show that ancestors of damselflies with 30-inch wingspans flew more than 300 million years ago! They had wingspans similar to the wingspans of pileated woodpeckers or small hawks. These giant insects flew tens of millions of years before dinosaurs roamed the planet, and 150 million years before flying birds evolved.

A blue-fronted dancer damselfly in the Cambridge Highlands on Aug. 21. (Photo: Kate Estrop)

Damselflies go through three stages: egg, a larva or nymph (a small adult without wings) and adult. Although we most often see the adults, this stage lives only days or weeks. Damselflies spend most of their lives – one to three years! – as tiny underwater nymphs.

The nymphs lie in wait until water fleas or small offspring of snails, worms, crayfish or clams swim by. Then their lower lip, with two hooks on the end, rockets out to snatch prey. You might see something like it in a sci-fi thriller.

Damselfly nymphs breathe dissolved oxygen in water using three bladelike gills that protrude from the end of their body. They can also absorb some oxygen through damp skin, so if oxygen levels in the water are low, the nymphs surface to the open air. The bladelike gills also function like a rudder, helping steer them through the water.

A tiny fragile forktail damselfly in Lincoln on June 7. (Photo: Norm Levey)

Damselfly nymphs shed their skin up to 15 times as they grow larger. During their last molt, they climb out of the water. Their skin splits down the back, and a winged adult emerges. They swallow air to pump up the wings and body, resting in the sun to dry out. The adult damselflies breathe through 20 holes (called spiracles) on the sides of their bodies, for they do not have lungs. The spiracles are connected to a tubular network that delivers oxygen to cells and collects carbon dioxide to be expelled.

The new six-legged adults move away from the water to sheltered areas where they feed on small insects, especially mosquitoes, flies and aphids. They often hover over low vegetation, picking off prey from leaves and stems (unlike dragonflies, who prefer to capture flying prey). Although adult damselflies are capable of living for 15 weeks, most damselflies die within a few days. Some die due to harsh weather conditions. Others are eaten. Birds, frogs, spiders, fish, dragonflies and salamanders all eat damselflies!

To mate, the male holds the female behind the head with the claspers at the end of his abdomen. The female curls her abdomen around to collect the male’s sperm. (Photo: Tom Murray)

Damselflies return to the water to mate, where males are very territorial, guarding their turf, chasing away rival males and approaching any females that happen by. The males recognize the females by their color patterns.

Damselflies have long, slender abdomens with 10 segments. Male damselflies have two penises – a primary one and a secondary one. Hundreds of millions of years ago, they had only one at the end of their long abdomen on the ninth segment, and that is still the primary penis in modern damselflies. At the other end of the abdomen, on the second segment near the damselfly’s midsection, is a secondary penis that stores sperm.

An Atlantic bluet in Somerville on Aug. 7, 2020. (Photo: Cody Matheson)

The male must fill his storage penis with sperm before he can mate. He does this by looping the tip of his abdomen in a circle to the storage penis at the other end of his abdomen to make the transfer.

Mating may be preceded by a courtship dance in which the male displays his wings, abdomen or legs to a female. The female pays close attention to the male’s coloration, size, ability to defend his territory and even his body temperature.

A fragile forktail damselfly in Groton on June 25, 2023. (Photo: Tom Murray)

To mate, the male grabs the female behind the head with claspers at the end of his abdomen. The female curls her abdomen around to collect the sperm the male has stored. (The female’s reproductive organs are at the tip of her abdomen.) The entwined bodies form a heart shape.

After mating, the male hangs on and flies in tandem with the female as she lays her eggs. He wants to prevent other males from mating with her. If a rival male is successful in dislodging the first male, the rival male scrapes out the first male’s sperm and deposits his own – all while the pair is locked in the heart formation.

The female lays eggs in plant stems or leaves in or near water as the male continues to hang on or hover nearby. The eggs hatch in two to five weeks, depending on weather conditions. Eggs laid in the fall suspend their development until spring, when temperatures warm.

A bluet in Lincoln on Sept. 27, 2020. (Photo: Norm Levey)

Damselflies, like dragonflies, have compound eyes made up of 20,000 to 30,000 photoreceptor cells (resembling a honeycomb). These eyes produce astoundingly clear images. They can spot prey from 40 feet! They can also see colors, such as ultraviolet, that humans cannot. In addition to their main eyes, damselflies have three simple eyes arranged in a triangle between their large eyes. These are light sensitive organs that help them follow movement.

The species’ flying ability is also fantastic. Their front and hind wings beat in opposite directions, which makes them highly maneuverable. They are among the fastest flying insects, and they can hover or fly backward.

An eastern forktail in Groton on May 22, 2022. (Photo: Tom Murray)

When you see dragonflies or damselflies near water, this is a good sign. It means the water is relatively unpolluted. Damselfly dependence on water is also concerning, because it makes these insects vulnerable as our wetlands diminish.

When the weather is cool (below 60 degrees Fahrenheit) or raining or windy, damselflies rest on vegetation instead of flying. If you want to photograph or take a close look at a damselfly, look early in the day when the temperature is cooler. Once the weather warms up, damselflies flit about so much that it is more difficult to get a close look.

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Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.