News

Dragonflies: Shimmering jewels of marsh and sky

Male 'Needham's Skimmer,' most common dragonfly on Ocracoke. (Females are yellow instead of orange-red.) Photo courtesy of Beechnutphotography.wordpress.com

Male ‘Needham’s Skimmer,’ most common dragonfly on Ocracoke. (Females are yellow instead of orange-red.) Photo courtesy of Beechnutphotography.wordpress.com

By D. Creeksong

Almost anywhere on Ocracoke in late summer you will notice buzzing bevies of brilliantly-colored dragonflies. Vibrant oranges and reds, lemon yellows with sparkling golden wings, dark-eyed dusky blues, grass greens with striped tails–the range of colors is phenomenal.

Valuable as well as beautiful, these striking creatures devour many insects, including mosquitoes, a fact well-appreciated by islanders. Philip Howard writes in his online Ocracoke Island Journal that they are known here as “skeeter hawks.”

Yet it is their unique life cycle that inspires awe.

Named Odonata Anisoptera, Anisoptera roughly translates as “unequal wings.”

Dragonflies are often confused with damselflies (Odonata Zygoptera, whose “equal” or matched wings typically fold overhead rather than spread flat at rest).  To distinguish between the two–if you are lucky enough to catch one at rest–look at their heads: with eyes spread wide and directly opposite each other, the damselflyʼs head has been likened to that of a hammerhead shark.

Perhaps the most peculiar aspect of the dragonfly world is the mating ritual, which begins with a male nabbing a female in midair. The capture is accomplished with his legs, just as he would prey, but the similarity ends there.

Claspers at the end of his body are then attached to the back of her head, both to keep other males from her and to prepare to mate.

This “in tandem” pose is not the sexual act, as is commonly believed. Instead, two more unique events precede actual insemination.

Just before, or shortly after the male has clasped her head, he transfers sperm from the end of his body to his “accessory genitalia,” located behind his legs.

'Green Darner' dragonflies mating. Female's legs are wrapped around the male's abdomen. Most common migratory species.

‘Green Darner’ dragonflies mating. Female’s legs are wrapped around the male’s abdomen. Most common migratory species.

The clasped female then bends her abdominal tip up to receive the sperm–creating the “wheel position.”  But the male will first engage a set of paddle-like appendages to scoop out sperm from any previous mating before depositing his own.

Eggs are laid in an amazing number of ways. Species with ovipositors (which are a type of egg-laying apparatus) cut slits in stems of plants or logs, inserting eggs within, or tuck them directly into a creek bed. Other methods include tapping out eggs on top of water as though enjoying a staccato beat, or letting loose an entire mass as one long sticky strand. Eggs are also laid in dry areas, going dormant until submerged with spring rains.

Once hatched, the resulting nymphs begin their process of maturation. Based on the species, this can take anywhere from two months to five years, including molting between 6 to 15 times.

Fierce hunters, nymphs come equipped with a toothed mouthpart whose length can be three times that of their head when shot forward to seize prey. Known for ingesting volumes of mosquito and other larvae, dragonfly nymphs have also been filmed eating tadpoles and small fish larger than themselves.

A dragonfly emerging from its larval exoskeleton is remarkably similar to a butterfly emerging from its chrysalis. However, the dragonfly must now adapt from using gills to breathing air. These first gulps of air will serve to begin the expansion of its new form and its new cycle of life.

From ancient petroglyphs to preserves throughout Japan, dragonflies have been revered for centuries. Recent research includes attaching radio transmitters to migrating species, then tracking them with Cessna airplanes. One dragonfly traveled 93 miles in a day.

To help with this research, please report all dragonfly swarms and dragonfly migration to https://migratorydragonflypartnership.org/index/about.

Entomologist Cindy Goforth, who works for the N.C. Museum of Natural Science, is also seeking assistance with her “Dragonfly Swarm Project” at https://TheDragonflyWoman.com.

Another view of a Male 'Needham's Skimmer.'

Another view of a Male ‘Needham’s Skimmer.’

1 reply »