Meena Haribal, a chemist at Cornell’s Lab of Ornithology in Ithaca, lugged the ancient office laptop down to the visitor’s area to show me her photos of her favorite animals: dragonflies and damselflies (Order Odonata).
“They are fascinating creatures,” she told me. “They have interesting behaviors, and they are beautiful to look at. Everything about them I like.” As she showed me her detailed photos, I wasn’t sure if I unreservedly agreed with her assessment. They are indeed beautiful from a respectful distance. But some of her remarkable close-ups did not depict my idea of beauty.
My reservations might have been even more apt 300 million years ago, when oxygen levels were 70 percent higher, when most insects were bigger, and Odonata, in particular, had a wingspread of two feet or more. Their larvae, 16 inches long, attacked anything they could catch and would have made stream and pond wading extremely unpleasant.
Of the approximately 7,000 species of Odonata, 110 have been recorded in Tompkins County, according to Fred Sibley, a retired Yale ornithologist, who currently lives in the county and studies dragonflies.
One simple way to distinguish these Odonata families: Damselflies are smaller than dragonflies and rest with wings folded back upon their abdomen; dragonflies and their even larger cousins, the darners, rest with wings outspread.
Haribal has observed 70 of these species. “The green darners come first to the region,” she said. “I spotted the first one outside my office window in the ornithology lab a few days ago [mid-April].” Aurora damselflies also arrive early in the Finger Lakes. They are gone by June or July. Canada darners, with blue–green stripes, are common patrollers of pond shores.
Fred Sibley spoke about another of our local species, the gray petal-tail found in Watkins Glen and Robert Treman State Park. “They’re similar to those in the dinosaur age,” he said. “They’re very large and tame. They’ll often land on a hiker’s head or shirt. They’re in their northern edge of range here.”
The early life of the dragonfly is biologically intricate, composed of many stages. It progresses from a nearly microscopic egg laid in water to a formidable bottom-dwelling nymph, hunting mosquito larvae, smaller nymphs, tadpoles and even small minnows. It catches prey with a lightning-fast snap of its toothed lower lip. In turn, the nymph is also prey to other water predators, especially fish.
If the nymph survives throughout its complex larval stages in the water, it eventually climbs out onto a plant or on shore, emerging as a vulnerable, soft fly –– land-bound for a few hours until its wings and body harden. At this point, it is easy prey for birds, frogs or other dragonflies. From egg to adulthood, dragonfly mortality rates could be as high as 90 percent.
Those that survive seek mates. Dragonflies have unique mating habits. When a male is ready to mate, he transfers sperm from his lower abdomen to a storage spot closer to his thorax. When a female of the same species comes nearby, the male uses the tip of its tail to lock onto an analogous “keyhole” structure on the head of the female. Then the female curves her tail up to receive the sperm from the storage area.
Many species mate in flight; others alight on perches. The males of several species continue to clasp onto the female until she has laid her eggs to prevent competing males from mating with her. Males of some other species release the female but stay close by to chase away any competitors.
As adults, dragonflies are carnivorous, eating every type of insect they can manage to catch. Haribal reported that while once holding a damselfly in her hand, a dragonfly swooped down to eat it. In turn, Odonata are eaten by many bird species, especially flycatchers. Sibley noted that the American kestrel migration coincides with the green darner migration because the kestrels depend on them for food.
Still, we know little about dragonfly migration. Our knowledge of Odonata is in its earliest stages. “Interest in dragonflies has blossomed in the last ten years,” Sibley said. “Before that, it dragged 100 years behind birds. If you want to see a parallel, look at bird books from the turn of the last century.”
Although dragonflies and damselflies are everywhere and easy to find on a sunny summer day, they often go unnoticed. If you want to observe Odonata, bring boots, binoculars, maybe insect repellent, and a guidebook to your favorite pond, stream or field, and just enjoy these remarkable insects.