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Wasps – truly venomous or just wanna-bees?

With borders having re-opened across Europe, there has been a giant sigh of relief; summer holidays and travel abroad are possible again. In light of this, it seems that many people have forgotten about the global pandemic and decided to embrace the idea of ‘ignorance is bliss’. Whilst hoping not to fall into that category, I nevertheless decided to take advantage of my newly gained freedom and travel to the south of France. Taking all the measures I could think of to stay COVID-19 aware and safe, I was able to enjoy sunshine, nature, and great food. However, I was also quite suddenly reminded that viruses are not the only thing to be aware of – venomous animals are all around us and we rarely give them a second (or even first) thought. This is something I hope to rectify with this post.

Illustration: Timothy Jenkins

Corona conscious summer holiday

I was staying at a friend’s old watermill nestled between two wooded hills, close to the Haut-Languedoc Regional Nature Park. Nature thrived and there was a constant humming and buzzing of insects. Particularly, the vespids (wasps and hornets) surrounding us caught my interest. There was the common European wasp (we all know these ones and what pains they can be – literally when particularly unlucky), less common paper wasps, some solitary wasps, and a few (very large) hornets. All of them loaded with an interesting arsenal of venomous toxins. In fact, if you are unfortunate enough to be envenomated at any point in your life, it will most likely be by one of these vespids or by bees (not spiders or snakes). The good thing about vespid venom is that it won’t kill you, as long as you don’t suffer from a severe allergic reaction. Nevertheless, it will hurt – a lot.

Illustration: Wikimedia

The four types of vespids I saw in France. A common European wasp (top left), a paper wasp (top right), a solitary wasp (bottom left), and a hornet (bottom right)

Insect and particularly vespid envenomations can be incredibly painful. Luckily, a crazy American entomologist decided to dedicate his life to investigating just how much the different stings hurt. His name is Justin O. Schmidt and he dedicated his career towards the classification of the stings of 78 species and 41 genera of Hymenoptera (i.e., bees, ants, and wasps). He did this by getting himself stung (of course – he is American after all) and came up with a classification where he ranked all his experiences from ‘meh’ (= 0) to ‘Hell no!!!’ (= 4), which has been beautifully visualised in the graphic below. I highly recommend reading more about Schmidt’s experiments here.

Illustration: Lauren J. Young

Illustration of the top 30 most painful species according to Schmidt’s pain index

As you can see, the above-mentioned paper wasps (numbers 10, 18, 19, and 21) feature prominently in the top 30 and, unfortunately, I can vouch for the truth of this assessment. During one of the courses of my Zoology undergraduate degree in Australia, we went on a field trip to a nearby rainforest. We were given some basic insect-catching equipment and were told to collect some creepy-crawlies, so we could identify them back in the lab.

Illustration: Wikimedia

Rainforest much like the one where I encountered “stingless bees”…

We all happily ventured off into the forest and started collecting a few beetles, ants, and whatever else we could find. Towards the end of our ‘search-time’ I came across a weird object dangling from a branch at head height. It looked like a native stingless bee nest, which as the name suggests, is harmless. I spotted one of these bees on the nest and decided (in my infinite wisdom) to scrape it off into my plastic jar. That all worked out great, until I suddenly heard a deep humming and the whole football size nest started vibrating. A dark cloud of hundreds of these stingless bees emerged and flew towards me, which despite the lack of stingers was quite intimidating. I turned tail and ran towards the edge of the forest, where we were supposed to meet – the cloud followed, and some individual bees soon caught up. I suddenly felt like I had been shot by a gun, with sharp intense pain radiating from my arm. I quickly realised my idiocy; these were not stingless bees, but the infamous paperbark wasps (Ropalidia romandi). At that stage I had reached my classmates, but so did the angry swarm of wasps (sharing is caring after all). Mayhem ensued and let’s just say my popularity dropped somewhat after this event, especially since some of my friends ended up being stung way more than me. The scientist in me wanted to know a bit more about these wasps once we got back from our field-trip and this is the official information I found on the Queensland Museum website: “Mostly people are stung when a paper wasp nest is disturbed, or the wasps feel their nest is threatened (did that...). The wasps will swarm out, pursue the intruder, and may inflict multiple stings (check that one off too...). Stings from paper wasps are immediately painful and the site of the sting may remain itchy and swollen for days (all good things come in threes...)”. It sounded like my experience was a model example after all.

Illustration: Queensland Museum

Paperbark wasp and a nest, much like the one I decided to disturb

Fortunately, I dodged that bullet during my vacation in France, but my host was less lucky. One afternoon, as he sat down on his chair, he disturbed a hornet, which decided to retaliate by stinging him in his forearm – not a pleasant experience, with the pain lasting for over three days.

Illustration: Timothy Jenkins

The place we were staying at in France and the impact of the hornet sting on our friends left arm (red and swollen)

So why are these stings so painful?

A vespid sting is biochemical warfare on a molecular level and serves two purposes for the animal: 1) It immobilises prey so it can be easily transported back to the nest for a family feast and 2) it can induce enough pain to deter larger animals and potential predators. The way vespids cause such pain, despite being so small, is by hijacking our nervous system. Pain is one of our body’s security systems and functions a bit like the alarm system you would use to protect your house. When an intruder is detected, it goes off to make you aware of this potential danger. In our body, this alarm system works via nerve cells (neurons) that signal danger to the brain. Wasp venom takes advantage of this molecular signalling mechanism and fools our body into thinking that it can cause a lot more harm, than it actually can.

The first step is the venom being injected via the stinger. Immediately, toxic peptides and enzymes in the venom break down cell membranes, spilling cellular contents into the blood stream. Some of these cells will be neurons, which will rapidly signal to the brain that they are being damaged and destroyed. This causes pain. To make sure that its efforts are concentrated, and the pain keeps coming, the wasp or hornet venom also contains other molecules, such as norepinephrine to slow the blood flow. The better the venom is at doing this, the longer the pain will last, since it delays the dilution of the venom. The final key components are hyaluronidases and MCDPs (mast cell degranulating peptides), which essentially melt connective tissue to allow the membrane-destroying toxins to move onto other cells. This is where swelling and redness associated with most insect stings originates from. The particularly nasty thing with vespids is that – unlike bees who sacrifice themselves for the greater good and die after inflicting a sting – vespids can sting you all day long (though the venom might run out at some stage). However, vespids aren’t all evil. They do try and warn everyone that they are not to be messed with by displaying bright colours – this works for most animals but not so much for humans.

The logical follow up question is what should you do if stung?

The good news is that while most stings are painful, they’re also harmless. The bad news is that there isn’t much we can do to treat them. Common advice is to:

  1. Clean the sting area with a medical disinfectant to prevent infection (no excuses – everyone should have some disinfectants thanks to COVID-19).
  2. Cool the area to help reduce the swelling. You can use an ice pack wrapped in a towel.
  3. Take some light anti-inflammatory agents and pain killers if the pain gets too much.

However, if you get more severe symptoms, e.g. have trouble breathing, you should call an ambulance or head to a local emergency room immediately, since you might be having a severe allergic reaction.

Given these facts, the question posed in the title of this blog entry should be easily answered – wasps and hornets are venomous, and they can pack quite a punch. However, at least next time you are stung by one of these critters, you at least now know what fascinating biochemical process is unfolding in your body - Yay!

Timothy Jenkins holds a PhD in biomedicine and is an aspiring biotech entrepreneur. He recently completed his doctoral studies at the University of Cambridge, where he was awarded the ABCAM award for top PhD candidate at his department. Now, Tim is working as a postdoctoral fellow at the Technical University of Denmark with biotechnology-based antidotes to snake bites. Timothy Jenkins har en ph.d. i biomedicine og er biotek-entreprenør in spe. Han er uddannet ved University of Cambridge, hvor han modtog ABCAM-prisen for bedste ph.d.-kandidat i sin afdeling. Nu arbejder Tim som postdoc fellow på DTU med biotek-baserede modgifte mod slangebid.
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I have on a couple of occasions been unattentative enough to accidently squeze a wasp under my feet and under my hand. Very understandable on both occasions the wasp stung me in order to avoid certain death and live out its free and happy wasp-life. And yes, it does hurt but not all that bad. The first time I was a kid around 8-9 years old and my mother applied the surface of a freshly cut onion to the sting, which made the pain go away after only 3-4 hours. The second time I didn't do that, and the pain lasted the rest of the afternoon.

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Great article. Just wondering why the norepinephrine. If you want to paralyze food, wouldn't you want the venom to circulate rapidly? Or does norepinephrine have no effect on inverterbrates?

Do we know which component paralyses the wasp's prey?

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Hi Jens, thanks for reading the blog and sharing your own experience. I definitley agree that there is a wide variation in terms of pain that different wasp stings cause (also quite nicely described in the Schmidt index figure I posted). I have never tried using onions on stings, but after your comment looked into it a bit. It seems that fresh cut onions (and presumably onion juice) contain an enzyme that can break down pro-inflammatory molecules, such as the ones present in bee and wasp venoms. I couldn't find any clinical trials on it, yet one medical article suggests onions as a way to treat stingray wounds (Medical Journal of Australia, June 1, 1998). Also, it appears that onions are common sting remedies among Turkish beekeepers (International Forum of Allergy & Rhinology, July 2014). So, I will definitley give it a shot when I (inevitably) get stung again.

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Hi AL Dante and thanks for reading the blog. Very good questions that I will try to answer with the following:

1. Why the norepinephrine: Purely for defense against mammals. As you correctly suggested, it doesn't affect invertebrates. Invertebrates have a homologue (Octopamine) that fulfills the same role, but the receptor is different enough that doesn't bind. 2. Which component paralyses prey: The ability to fully paralyse prey is particulalry common in solitary wasps (notably the great majority of known species of Hymenoptera are solitary wasps). Their venom is applied much more against other insects than that of the honeybee and social wasps. A 'nice' example is the bee wolf (Philanthus triangulatus) that paralyses worker bees to provide live food for its larvae. The paralyzing substance was found not to be a peptide but a butyryltyrosine derivative of a polyamine, philanthotoxin-433 - inhibitors of the nicotinic acetylcholine receptors (much like many snake neurotoxins).

However, there are many other neurotoxins that have been isolated from wasp venom (some insect specific):

  1. Bradykinin-related peptides are presynaptic blockers of nicotinic acetylcholine (nACh) receptors in the insect CNS and may induce smooth muscle contraction in mammals.

  2. Pompilidotoxins (Anoplius samariensis and Batozonellus maculifrons) block sodium channel inactivation in both vertebrates and invertebrates.

  3. Philanthotoxins (Philanthus triangulum) block postsynaptic glutamate receptors and nACh receptors.

  4. Microbracotoxin (Microbracon species) is a presynaptic neuromuscular signal blocker that causes irreversible flaccid paralysis in lepidopteran larvae.

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