Ask The Entomologist

Wasps… they’re not always out to get us.

What says midsummer better than unexpected wasp nests? Buzzing uncomfortably overhead, nests full to bursting with developing young. Dreadful things, right?

What would you say if I told you that aggressive wasps (think of your stereotypical Bald Faced Hornets) aren’t the only kind out there? Even within a single species, there are a wide variety of levels of aggression.

If a wasp is going to be aggressive to protect her nest, full of her offspring and her sisters’ offspring, she really has to go all out. If a wasp doesn’t give her all when driving potential threats away, chances are that the nest will have to repel more attacks, and the nest will be more likely to be detected by more dangerous predators! Predators who will attack and destroy that nest, despite angry wasps and stings. Both mammalian predators (bears, humans, etc.) and insect predators (especially ants!) are more likely to attack nests that reveal themselves by being aggressive.

While bears are stereotyped as being very fond of bees’ honey, they also relish eating the “brood”. “Brood” are the developing larvae or pupae that will grow up to become wasps or bees. While you can only get honey from some sorts of bees… you can get delicious brood from any active bee or wasp nest!
Think of snacking on sugary fresh fruit… now think of eating a ham sandwich… Which one makes you feel more full? Bears, especially young ones, love protein-rich young insects.

There’s another strategy for survival. What if the wasp was sneaky, stealthy, and conflict-avoidant instead of being crazy aggressive? It turns out that this is a valid strategy for survival, too. Think about it – if nobody knows the wasps are there, nobody will be trying to eat their brood!

Different colonies of the same species of wasps often vary widely in how aggressive they are! Not all paper wasp nests are terrible… I’ve certainly met some aggressive ones when cleaning roof gutters and peeling off siding, but I’ve met others of the same species who wanted nothing more than to escape notice! Look at this nest, tucked below the hinge of our vehicle’s front passenger door:

These wasps had no interest in attacking us – I got within 3 inches of them with my camera, and none made threat displays. I only noticed them because I saw the same species of wasp flying outside of the vehicle as we started it up… I saw these wasps several times in a row, despite it being parked at different places… including some where this particular paper wasp isn’t common. The wasps were being sneaky – they’d found a warm place to rear their young, inside a protected shell that ants and bears alike would be unlikely to spot them in. And it worked out well for them… until I saw them and decided that I didn’t want them meeting the dog.

Next week: How to read a wasp’s body language. Apologies, folks, wasp control instead.

3 thoughts on “Wasps… they’re not always out to get us.”

  1. Is it true that once stung by a wasp, you then give out a scent that tells other wasps to attack and if so, how long does this scent last. I’ve recently had a bad experience with a wasp.

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    1. Hi, Shari,

      It is true that many social wasps, including paper wasps, release an alarm pheromone when they sting (or when they are crushed). Some of that alarm pheromone remains at the sting site. Fortunately, alarm pheromones are for quickly provoking strong responses and don’t stick around. Pheromones for marking territories or trails tend to last much longer.

      Think about it – it’s not a good use of resources to have law enforcement on duty at a single crime scene after the issue is dealt with. Threats tend to last a short while, so alarms should as well. And if threats return, more alarm pheromones will be released.

      I did some research, and nobody seems to have measured how long the alarm pheromones of our common paper wasps last. However, we can assume they dissipate quickly, based on studies examining other related wasps, as well as ants and bees ( https://en.wikibooks.org/wiki/Animal_Behavior/Pheromones_in_ants_and_bees ; https://www.sciencedirect.com/science/article/pii/S0083672910830195 ).

      The unrelated Southern Yellowjacket is an example with an “unusually long-lasting alarm pheromone” ( aggressive response to pheromone after 15 hours – https://journals.flvc.org/flaent/article/view/59540/57219 ).

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