125: Odonata, Dragonflies and Damselflies
I was riding my bike the other day when I noticed a dragonfly hovering above the South Platte. Every time I see them, I am in awe of how long they have been around – their ancestors date to the early Carboniferous, millions of years before the time of the dinosaurs. One of their ancestors, Meganeuropsis, is the largest known insect of all time, and lived around 290 million years ago, which had a wingspan of over two feet! Although modern dragonflies and their fellow Odonata order members, damselflies, have evolved since that time, they are still visibly similar to insects that flew before the existence of flowering plants.
During the time that dragonflies and damselflies were first evolving, Colorado was part of the supercontinent Pangaea. Sandy deserts covered what is now our state, and we can still see the remains of that landscape today in the Lyons formation, red sandstone along the Front Range that makes up part of the dramatic formations at Garden of the Gods and Roxborough State Park.
Today, dragonflies retain an ancient wing structure, meaning that they are not able to fold their wings up against their backs. They can fly at speeds up to 30 mph. Damselflies, in contrast, do keep their wings folded on their backs; they are also smaller and slimmer than dragonflies. Dragonflies are powerful fliers, while damselflies have more of a stuttering flight. They live on every continent except Antarctica, and there is even one species – the treeline emerald – that lives above the Arctic Circle. They each have two compound eyes consisting of a different number of ommatidia (clusters of photoreceptor cells) based on species.
Both dragonflies and damselflies are carnivorous, and they are very, very good at being predators – studies show that dragonflies, who capture their prey (like flies) in midair, succeed 95% of the time. Lions, meanwhile, succeed in their hunts about 25% of the time. Even I, a very specialized predator indeed, will wander into the kitchen and wander back out without having chosen food more than 5% of the time (I’d estimate about 20% of the time). According to the article linked above:
In a string of recent papers, scientists have pinpointed key features of the dragonfly’s brain, eyes and wings that allow it to hunt so unerringly. One research team has determined that the nervous system of a dragonfly displays an almost human capacity for selective attention, able to focus on a single prey as it flies amid a cloud of similarly fluttering insects,.
Other researchers have identified a kind of master circuit of 16 neurons that connect the dragonfly’s brain to its flight motor center in the thorax. With the aid of that neuronal package, a dragonfly can track a moving target, calculate a trajectory to intercept that target and subtly adjust its path as needed.
As a rule, the hunted remains clueless until it’s all over.
“Before I got into this work, I’d assumed it was an active chase, like a lion going after an impala,” Combes said. “But it’s more like ambush predation. The dragonfly comes from behind and below, and the prey doesn’t know what’s coming.”
In Colorado, we have 106 species of Odonata. If you’d like to try to see them all, here’s a handy checklist. Many of these species moved here in the second half of the 19th century, as European-style agriculture created more standing water sources, especially in the eastern parts of the state, which attracted native midwestern Odonata to the suddenly wetter environment. Very few Odonata live in the high mountains that make up the central portion of the state, and the mountains form a barrier between the eastern and western sides of the state for Odonata, with very different species found even in similar environments on the east and west of the high mountains.
I tried out a new program to make today’s drawing, Adobe Fresco. Anyone have experience using that? I’m not sure it’s too different from Procreate.
