Insect Picture of the Day

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Andrew Lin sends us this great picture of a damselfly. I’m not sure on the exact species, possibly a bluet?

What I do know is that the picture is well-composed and beautifully taken. Here’s the wallpaper to prove it.

Thanks, Andrew!

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Before you let your teenage damselfy go out at night, you need to know: Where is she going? Who is she going to be with? What will she be doing? You’re the parent. You need to know these things.

Because if you don’t know, she could be hanging out with carp.

They eat damselflies, okay? This is a bravery stunt about to go horibly wrong.

Thanks are due to Athena Fritz for sending this one in. Sorry for the mega-zoom-out here. You may need to uses the larger version to even see the damselfly. She’s the flash of blue at the center.

It’s impossible to make a positive ID at this resolution but I think it might be Argia vivida or a related species. They’re pretty common and match the markings here.

Thanks Athena!

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This is Argia Vivida, the Vivid Blue Damselfy. This photo was taken with the lens about 6cm away from the damselfly. My Dad had accompanied me on this trip and as I crept closer and closer, I heard him mutter, “They just let you get that close?!?”

The secret to stalking dragonflies and damselflies is to understand how their eyes and their brains work. The eyes are compound and without lenses, which means that, like pinhole cameras, they have no focal depth: everything appears to be in focus, near and far. This means they have no focal cueing to determine if an object is approaching or receding; they have to rely on motion detection for this. As we grow to understand image processing in the brain better and better, one thing we find is that motion detection and shape recognition are relatively easy things to do for even a small number of neurons.

The trick, then, is to not change shape. By approaching a dragonfly straight on, the only change in my appearance to the dragonfly is that my shape gets slightly larger. Since this happens very slowly, the dragonfly’s tiny image processing cluster files me safely away as harmless background.

I explained this softly to my Dad as I eased in for still closer pictures, and then I quietly announced, “Now watch, this will scare him off.” I reached my fingers around the camera to adjust a knob, and sure enough, he zipped off to safer haunts downstream.

The other secret to stalking dragonflies and damselflies is to remember that they are very territorial. I had enough pictures of him that I could afford to scare him off, but whenever I scare a dragonfly off, if I want more pictures I just sit quietly and wait. They inevitably return to resume the photoshoot.

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Remember when I said you could get damselflies to land on your finger? This beautiful narrow winged damselfy perched happily on my thumb for a few minutes, giving me the perfect photo op. She was flying along the length of my garage door, landing and taking off again. She didn’t quite look like she was hunting, but she didn’t seem satisfied with the purchase on the door. She looked, in short, like a damselfly who needed a good finger to land on!

No sooner had I presented my hand but she landed on my thumbnail. Once stilled, I immediately saw what she wanted: a quiet branch on which to eat her freshly caught breakfast! She happily sat still for the camera and munched on her bug. In this shot she’s all finished and about to fly off. And yes, if you look closely, you can see one of her victim’s legs wrapped around her eyeball.

She was a delicate little thing, barely 22mm long. Her head, as viewed in this shot, is maybe 4mm wide.

BONUS PICTURE!

Here’s a picture of this damselfly right after she first landed, showing her mostly uneaten prey. Please forgive me for captioning it–I couldn’t help myself.

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This green damselfly stopped in my yard for a quick breather after a long day of hunting. It was too skittish to land on my finger, but this species is especially amenable to the finger-landing trick.

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This blue damselfly is a male argia vivida. Damselflies are generally smaller than dragonflies, although this damselfly is actually a bit longer than the meadowhawk from last Wednesday. For the casual observer, the easiest way to distinguish dragonflies from damselflies is that damselflies fold their wings back when they land, while dragonfly wings stay locked in the flat and level position at all times. In flight, damselflies hover and will fly zig-zag “scanning” patterns over walls and bushes looking for bugs to swoop down on and eat, while dragonflies generally hunt at full speed, zooming forward to catch slower-flying prey.

Damselflies like to find vertical twigs to land on and rest between hunting spells. The next time you see a damselfly scanning a wall, point a finger straight up and move your hand slowly near it. If it’s feeling tired, it will light on your finger!