Showing posts with label hornets. Show all posts
Showing posts with label hornets. Show all posts

Jan 11, 2017

Tropical Nasties: Asian Hornets

Pure Evil!!!! aka the Lesser Banded hornet (Vespa affinis)
Last September I had an unfortunate run-in with a nest of Lesser Banded hornets (Vespa affinis). I had let a wooden crate weather in the sun over the Summer by leaning it against the garden wall. When I went to pick up the crate I unknowingly disturbed one of these:
Nest of the Lesser Banded hornet (Vespa affinis)
Yes, it was a not so proverbial hornet's nest. And as the proverb goes out came an onslaught of hornets which attacked me. Hornets, like many social wasps, can mobilize the entire nest to sting in defense by releasing an attack pheromone. Any materials that come in contact with this pheromone such as clothes, skin, and dead prey or hornets, can also trigger an attack. (Other aromatic chemical compounds such as banana or apple flavorings can mimic the effects of this pheromone too.) Bibi unwittingly disturbed the nest and thus became the target of a hornet attack. The entire neighborhood was treated to Bibi running and screaming blue murder across the yard. 

The unbarbed and nondetachable hornet's sting
Hornets can and do sting repeatedly. Hornets do not die after stinging like bees because their stingers are not barbed and therefore are not pulled out of their bodies. I can attest to this as I was stung 15 times. Rolling on the ground, removing articles of clothing, and soaking myself with a hose did not deter these damned things. My husband finally beat them off me with a towel. 

Acetylcholine, a neurotransmitter and active component mediating pain in hornet venom
Hornet stings are more painful to humans than wasp or bee stings. I can attest to this also. Out of all the creatures I have been stung by (bees, yellow jackets, fire ants, catfish barbels, and various species of mosquitoes), the hornet stings were the most painful. Insect venoms are a complex mix of proteins, peptides, enzymes and other noxious compounds. Hornet venoms differ from bee and wasp venom by containing about 5% acetylcholine. Acetylcholine is a neurotransmitter that’s also produced by our bodies, but in hornet venom it stimulates pain receptors thus heightening pain. Cytotoxic enzymes in hornet venom such as hyaluronidase and phospholipids A and B dissolve cell proteins allowing further penetration of venom into tissues. Serotonin, dopamine, and noradrenaline are present in hornet venom increasing pain and irritation too. Various histaminic compounds and other kinins contribute to pain and itching in the odious chemical cocktail of hornet venom. To me it felt as if a white hot nails were being driven into my flesh for about nine hours. The sting sites swelled to about the size of fried eggs being about four inches across and about an inch high. The handful of cetirizine, diphenhydramine, and ibuprofen I took did not help at all. I could not walk on my right foot that had been stung twice nor bend my right knee which had five stings on it for ten hours.  

Typical pockmarks from hornet stings, the cytotoxic venom has dissolved the flesh around the sting
The next day the cytotoxic and histaminic effects of the hornet venom really kicked in. Although the pain subsided I was left pockmarked and itching like crazy. The miserable swelling and itching continued for about a week and was not responsive to antihistamines nor NSAIDS. After about two weeks the swelling and itching reduced and I was left with fifteen little round scars. 
The Giant Asian hornet (Vespa mandarinia) or 'yak-killer'
Asian hornets cause many human fatalities worldwide. Here in Nepal they cause about 10 to 20 deaths annually. (Three children died in western Nepal last Summer as a result of hornet stings received while chasing monkeys out of a cornfield.) The Giant Asian hornet (Vespa mandarinia) is thought to cause 30 to 50 human deaths yearly in Japan. Between July and September 2013, hornet stings caused the death of 42 people in China and over 1,500 injuries. The fatalities are not all from allergic reactions or anaphylactic shock. At high enough levels hornet venom can cause multiple organ failure. Renal dialysis is the only way to remove the venom and it's toxic byproducts when they reach such high levels. 
Lesser Banded hornet killing a honeybee (via Wikicommons)
Asian hornets kill beneficial insects such as honeybees and preying mantis to feed their nesting larvae. I've seen Asian hornets hanging around the local fruit stands simply to kill the bees the ripe fruit attracts. I've also seen Asian hornets hanging around dead animals preying on the numerous flies. Supposedly Asian hornets eat ripe and rotting fruit but I've not see them do it. Apparently Asian hornets have spread as far as France (via a shipment of Chinese pottery) recently and have been spotted in the UK threatening domestic bees and humans.

Buh bye hornets!
So Bibi developed an eradication program of her own. In Viet Nam, Laos, and Cambodia hornet larvae are made into a tasty stir-fry and adult insects are used to to flavor alcoholic drinks. Bibi decided to go for a full tilt boogie BARBECUE!!! That's right, some paper rubbish piled onto the nest and the wooden crate, a pint of kerosene, and a match,  ~et voila!~ it was hornet flambée! Nasty bee and baby killers gone forever from Bibi's yard!

You can come out now, Baacha Khan. Mom is ok.
About all you can do to prevent hornet attacks is avoid them. Asian hornets breed during August and September so are likely to be more aggressive during these months. In general they will not attack you unless you disturb their nest, kill one of them, or are wearing a scent that attracts them. Even though the nests are about the size of a soccer ball they can be hard to see as they can be located underground in deserted rodent dens, amongst brush piles, dangling from canebrakes, up high in eaves, or even behind crates as Bibi found out. It is recommended not to run or flail your arms if attacked but rather walk calmly away. (Easier said than done.) If you are allergic to bees or wasps have your epinephrine injection at the ready if stung. If you incur more than ten stings it is recommended you seek medical attention. If you suffer 75 or more stings you are probably going to need renal dialysis and a few months' hospitalization.

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