My quick (Tweet-sized) response to this concern over biting and stinging is that odonates do neither to people. If you’re content with the abridged response, you can stop reading, stop worrying about dragonflies inflicting pain, and you’ll be fine. The whole story is a bit more complicated and, I think, more interesting. If you’re curious, continue reading…
Now, it is true that all odonates are predators and that they have formidable, shredding mandibles which make quick work of their meals. If you’ve never looked at the mandibles of a largish species with a hand lens or microscope, you should—they are impressive. It is also true that when you handle an odonate, they frequently reveal their mandibles (by flexing the labrum and labium) and repeatedly open and close them. This is no doubt a reflexive response to being in the grasp of a “predator”.
If those mandibles happen to come into contact with the handler’s skin (particularly the softer webbing between the thumb and index finger), they will close. It is usually more startling than anything else when it happens, but the larger species can inflict a painful pinch and even break the skin sometimes. They will all try it, but the small species (especially the smaller damselflies) have mandibles which are too small to grab the skin and their nibbling feels a little ticklish at worst. When someone receives a painful bite, it is their own fault because they handled a dragonfly in such a way that mandible-to-skin contact was possible.
|An ovipositing female Paddle-tailed Darner (Aeshna|
palmata). The arrow points at the "stinger".
Technically a person can be “stung” by a dragonfly, but it is very rare, and is never committed with the intent of causing pain. This happens when someone’s leg is mistaken for a log or tree stump by a female darner who is just looking for a place to lay eggs. I’ve only heard of it happening a few times, but I would guess that stories of huge stinging dragonflies are more frequent among anglers who often sit along the shores of lakes and streams with bare legs. I have also heard that it is rather painful which doesn’t surprise me.
I have never heard of anyone being “stung” by a damselfly. I presume it is possible, but I think most of them are too small to pierce the skin. The large spreadwings (Archilestes) have hefty ovipositors good for inserting eggs into woody willow and alder branches, and I imagine that they would be up to the task if so inclined.
Several years ago a female darner landed on my jeans just below the knee and started to lay eggs in the fabric. She seemed oblivious to my head and arm movements until I shooed her away—it was interesting and fun to watch, but I didn’t want her to waste her eggs on my denim. I wonder if I would have been a stinging victim if I had been wearing shorts instead, but I like to think that all the hair would have clued her in.
So, that’s the whole story on biting and stinging odonates. The thing to remember is that a free-flying dragonfly will never bite you. Even if it lands on you, it will not bite. Though stinging, technically, can happen, it is extremely rare and it is never done as a defensive or malicious act. Even if you swat at a dragonfly that is too close for comfort (why anyone would do that, I don’t know), it will never bite or sting as a defensive measure as yellow jackets and honey bees might when they are agitated. Odonates will simply fly away.