Tuesday, December 14, 2010

Do Dragonflies Bite or Sting?

I am regularly asked at talks and workshops whether dragonflies bite or sting. The question is posed frequently enough that it is included on a Frequently Asked Questions slide, and I figure that enough people wonder about it to warrant a blog post. This concern doesn’t seem to apply to damselflies necessarily, probably because most of them are small and seem less threatening, but in this post I’m referring to all of them—odonates.

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".
What about stinging? The females of some odonates are equipped with what could be described as a “stinger”, but this is used strictly for laying eggs—never as a weapon. These are sharp, sickle-shaped blades (known as gonapophyses in geek-speak) which are used to incise an opening in plant material where an egg is inserted. All odonates which lay their eggs endophytically (within plants) have this equipment. This means all of the damselflies and, among North American dragonflies, only the darners and petaltails.

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.

24 comments:

  1. Hi Jim, I'm delighted to see that you plan to blog. I've learned a lot from you on an individual basis and look forward to learning more.

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  2. Jim,
    I have wondered about this for quite a while and am now well informed. Thank you for this interesting information.

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  3. Thank you for this information! As a child I roughly grabbed a huge dragonfly and it bit me. No one believed that it could have bit me, and I grew afraid of these majestic bugs. Now, understanding it did bite, and why, I can go back to enjoying them. From now on, I will be glad to watch them, no touching! Thank you!

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  4. Hi Jim, my daughter just happened to be the victim of those mandibles. I got a picture right when it was biting her. It left her with a fine line where she was bitten.

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  5. I love dragonflies and damselflies. We have them in abundance here on Vancouver Island. I love it when they land on me in the sunshine and we sit together a while. Last summer I was hanging clothes out on the line and felt a prick on the back of my leg and turned to see a large green dragonfly and was so surprised. It flew away immediately. I finally remembered to look it up just now. Wondered if I had been "tasted" or what! First time that had ever happened. Thank you very much for your blogspot and answers.

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  6. i was sitting outside (on my porch) just now & a dragon fly landed on my face i didn't know what it was so i swatted away from my face & it bit my right under my eye. It hurt like hell & im wondering if there's anything i have 2 worry about? any1?

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  7. @Anonymous No, there's nothing to worry about at all. They have no venom and they don't transmit any diseases.

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  8. hey as a kid I was told if a dragonfly stung me it would turn my eyes green so I have always been afraid of dragonflies and after reading this I guess I was just lied to as a kid lol

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    1. Yes, and it probably wasn't the only time!

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  9. This evening I saw a large dragonfly that was trapped against the glass wall of the train station. I picked it up to carry it outside, in my cupped hands. And wow, the dragonfly really didn't appreciate this and chewed my fingers and palm in the 30 seconds or so it took to take him back outside. It even drew a spot of blood. I can't blame the dragonfly for biting, and it flew away quickly once I took him outside (hopefully not right back into the station). So, is there a better way to handle one in such a situation? I suppose I could have grasped it right behind the wings, but I didn't know he'd be able to chew my closed hand so vigorously and I wanted to act quickly! No harm done, I just washed my hand when I got home and can't see any marks now. I was impressed by the little dragonfly's persistence & feistiness.

    I'm enjoying your blog entries Jim. I was at Lake Martin Louisiana last summer; what a wonderful place for anyone who likes swamp birds, insects, gators, etc.!

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    1. Hi Diane,

      Yes, if you present the opportunity, they will nibble. You want to hold them by pressing the wings together over the back. They can't make contact with their mandibles if you hold them there. I'm glad you like the blog--I've been behind and I need to get back to it!

      Jim

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  10. Hi Jim,

    I really appreciate the post. I was on holiday a few years back and went to an outdoor swimming a few times. There were lots of dragonflies around the pool who quite menecingly hovered around me staring me the eyes. I was sure they were planning some kind of attack. I'm about to go back on holiday and have been having second thoughts about the outdoor pool. So this post is quite reassuring. Although I still find the way they fly intimidating it's good to know they are probably just curious rather than vicious.

    Thanks.

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  11. I was hiking as a kid near Seattle, and was stung by two tiny dragonflies on my bare leg before the day was done. I'm not sure what they are called, but they are everywhere in the NW. I've shoed them away since then. I'm hoping now that I know they don't attack and aren't venomous that I won't be so bothered when they are near. Thanks!

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  12. Hi Jim,
    I wanted to find out about dragonflies, for my boyfriend, and found your article. He's in Ontario and has a huge pond and has noticed a large amount of dragonflies hanging about lately. He was curious about what they eat, etc. Now we know. As for myself, I've always been afraid of them; they're so big and I never knew if they were a biting insect. I will now be less afraid of these cute little creatures. Thanks so much, Irene in B.C.

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  13. Kristoffer Van AttenJuly 19, 2012 at 3:11 PM

    This past week, while floating in Lake Powell, AZ/UT, a dragonfly mistook my hand for a nice place to lay her eggs. She poked me with her ovipositor about five times before I really felt it (kind of like a horsefly bite), as I was dumbstruck by the idea of being stung by an odonate. She raised six large welts, but they quickly went away. Thank you for your info!

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  14. Thank you for this informative post.
    Yesterday my husband and I were at the Spokane River and saw a pair of dragonflies, flying hooked together (presumably mating). They tried to land on us but we shooed them away gently. Next thing I know I felt a sting, almost like a biting fly, and I yelped and looked at my shoulder only to find the **** dragonflies there. I brushed them off. This happened four more times, with them landing on me in various places and biting/stinging. I wouldn't see them approach, but was only alerted to their presence by the fact that they gave a good bite (or sting). I am not sure if it was the same pair each time or not. Does the ovipositing female try to lay eggs while still attached to the male? I thought this behavior was very odd and definitely painful. I was so surprised to have been "bitten" by a dragonfly that I came searching for an answer today. Mistaking me for a tree or something was their mistake. Now something I always liked and thought was a pretty little insect I have a good deal of malicious feeling toward.

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    1. Damselfly pairs often oviposit tandem. It's pretty common. I hope you still see their value as predators of other flying insects which are not so beneficial. Whenever I go looking for odonates, it's the mosquitoes, black flies, no-see-ums, and deer flies that I worry about. They're the ones that actually seek you out for a meal.

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  15. Well, reading this was confusing. At first, we were assured that dragonflies do not attack you, especially in the water. Then people said they were attacked. So I am still as confused as ever!

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    1. I guess that depends on your definition of "attack". As I described, they can bite, but only when mishandled, and they can "sting", but it's not a malicious or defensive act and it is rare (though perhaps that does happen more than I realized). I have yet to be "stung", and I actually go seek out dragonflies and damselflies much of the summer. Maybe it doesn't happen to me because I am always moving around as I look for odonates. They don't want your blood, and they don't defend nests (the way wasps do), and they don't come after you after being swatted (also like wasps), so in that sense I say they don't attack.

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  16. I found your blog very informative...I live on Long Island in NY and I have many dragonflies in my yard. I've always wondered if they stung or bit people and I was afraid of them. But now I understand more about them and I appreciate their beauty and enjoy sitting and watching them fly around. Although I will be a little cautious and make sure I keep an eye out for females thinking my legs are a tree. :) can you tell me what species of dragonfly I see here on LI..I live in Massapequa. Thanks for the info!

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    1. Hi Betty, I'm glad you found the post informative. I don't know much about the dragonflies in that part of New York, but you can check out the list of species known in the state at http://odonatacentral.org/index.php/ChecklistAction.showChecklist/location_id/55. If you click on the checklists tab at the top, you can drill down to particular counties in New York too. There is also a New York Dragonfly and Damselfly Survey report at ftp://ftp.dec.state.ny.us/dfwmr/nynhp/nydds/nyddspublicreport.pdf which may be helpful to you.

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  17. I holidayed in France a few years ago on a campsite that had numerous lakes, hence plenty of dragonflies. Walking across a bridge I looked down and noticed a dragonfly happily sat on my leg. I tried to encourage it to move on but it didn't. I then brushed it with my hand and it took off. Within a second my leg began to sting. By the time I reached our touring caravan it really began to hurt and a swollen red patch had appeared. It hurt for a further twelve hours or so, and it certainly was painful. The swelling took quite a few days to subside. It itched for a week or two later. I never realised such things could bite or sting. From reading this forum, it appears it may have been a female dragonfly but I don't remember it curling its tail, it was just sat, wings open, then it took off. Thankfully it didn;t attach itself to my young son who was with me, It would have a nightmare as the pain was very intense.

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  18. They don't bite, but everyone knows they sew your lips shut!

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  19. lol they are harmless

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