Wednesday, August 7, 2024
By:
It is time for the final blog, and I realise I have neglected to give you (dear readers) a general background on the biology of dragonflies. So, here we go: Dragonfly 101.
Week one, I told you that there are around 3000 species of dragonflies, in the order Odonata with damselflies. I said that dragonflies are characterised by their huge compound eyes, two narrow pairs of intricately veined wings, and elongated, sometimes iridescent bodies. You may ask, what makes a dragonfly, not a damselfly? Dragonflies are stockier, with shorter and thicker bodies than damselflies. All of a damselfly’s wings are the same shape and they rest with their wings together, whereas dragonflies hold their wings out at right angles to their body. Finally, you can look at their eyes. Dragonflies have eyes that touch, damselflies do not. Ten weeks in, and now we know that dragonflies are not damselflies.
Some insects are born twice, in a sense. Dragonflies, like many other living things, begin life as eggs. Depending on the species, this egg may be laid directly in the water, inside plant tissue, or on various stuff around the water’s surface. After some amount of time, dragonfly larvae emerge. These larvae, called nymphs or naiads, spend their first life underwater. They are functionally wingless and dull in colour, hiding them amongst the sediments and plants they live in. Like adult dragonflies, naiads are formidable hunters. Their faces have a structure called a “mask”, a disproportionately large mouthpart that has a set of fanglike pincers at the end. Depending on the species, the naiad stage can last two months to several years.
Naiads eat, grow, and moult. With each successive moult, its wing sheaths become more and more apparent. When it is large enough, the naiad stops eating and journeys to the surface. Poking its head out of the water, it adapts to breathing air. Then, it climbs up a plant and secures itself. Once anchored, the naiad’s exoskeleton begins to split and harden, the body curling backwards as it emerges. The naiad swallows air and pumps hemolymph, the insect equivalent of blood, into its wings until it expands and is ready to fly.
Adult dragonflies do not live long, spending their time hunting and mating. Mating dragonflies form a “mating wheel”. Sometimes, this looks like a heart flying through the air. Dragonflies are an incredibly significant part of the ecosystem and a bioindicator of freshwater health. Not only are they an important food source for other freshwater organisms, their requirements of stable oxygen levels and clean water. Because of this, they can tell us a lot about the ecological integrity of the ecosystem, especially about the connection of aquatic ecosystems to the land.
So, not only are dragonflies super awesome, full of physics, and super awesome, but they are incredibly important parts of our ecosystem. Conclusion? Everyone should be a dragonfly fan.
If you have read any of my blogs, you know I am a dragonfly fan. This is evident in this year’s SOCK, which I spent Monday, Tuesday and Wednesday packing. Good news: 100 boxes packed and I learnt how to use power tools (thank you, Charles and Victor). Tuesday, post-box-packing, some of us had a quick jaunt to the botanical gardens to see the recently bloomed corpse flower (which did not smell like rotten meat, disappointing). I then made too much tomato stew and cried because I had one egg left. The egg problem was soon solved by buying a half dozen eggs (yay!). Wednesday, I watched Jurassic World: Dominion with my cousins. Dinosaurs? Cool. Giant locusts? I just think they could have been more accurate. On Thursday, all 16 of us went to ACP to practise our presentations. It was the largest number of us to have been in the office since, ever. Then, Kai and I made a peach cake and hosted a potluck. There were too many pickles. Friday was presentation day! We presented, and presented some more, and presented some more. My grandpa fell asleep (Sorry, Jaden). Kai moved out, and I mourned. We packed and then went to dinner at Tonic. Saturday, I left DC. Thank you to Jaden, Jenna and Charlotte for helping me pack the car before my journey began. Sunday, I ate a bagel, took two naps, said bye to my grandparents, and then got on a bright and early 2 am flight home.
So, writing this from my dining room table, goodbye DC. Thank you, interns, thank you SPS team, thank you every dragonfly species ever. To quote Charlotte’s blog: When else will you be 21 in a new city with 16 other physicists as friends? Turns out, this summer.
This week’s dragonfly is the Great Blue Skimmer, Libellula vibrans. It is 2.0 to 2.5 in length and found near lakes, ponds, and slow streams in the eastern United States. It is one of the largest skimmers. The immature forms are brown and the mature forms are blue, and I think it is beautiful.
Maia Chandler