Written by Joe Ballenger

During the fall, we get a lot of questions about wasps…but not about wasps in nests.

Often, these are from people who work in construction or otherwise around heights. I know the sizing of the pictures below is a little awkward, but they’re sized this way to show the behavior.

I run a house framing crew and each fall i run into this same situation. We have a boom truck on site (crane), and when the boom is high in the air, wasps congregate all along the boom, but especially at the tip. They will swarm all around the boom, more so the higher it gets. As i lower the boom to ground level, the wasps dissipate rather quickly until they are completely gone within 10′ or so of the ground. If i then raise the boom again, the wasps return almost immediately.  They hang out wether the machine is running or not. Just wondering what is going on. Also, there is no nest in the boom.

I work in the communication tower industry and every year around late summer to early fall we tower climbers experience a phenomenon. Wasps will swarm up towers. As you can imagine, this can be very disconcerting, however they aren’t aggressive at all while they’re doing this. In 20 years of climbing I’ve never been stung. It appears they are in the mood for love and mating.

There are a lot of misconceptions about this phenomenon though — everything from the wasps being attracted to the RF (radio frequency) to being attracted to the galvanizing of the steel itself. Would you explain what they’re doing up there and speak to the hazards of climbers sharing space with hundreds of wasps?

We’ve written about wasp nests before, in a question about why wasps tend to die headfirst in their nests. To begin this story, I’d like to quote the last part of that article.

These wasps are caught out in the cold-both figuratively and literally-after their society collapsed. After the annual collapse of their society, they died looking for food.

This sort of behavior is actually very common in social insects. Honeybees do the same thing. After winter, it’s very common to see dead bees headfirst in honeycomb. They died the same way…looking for food.

While these wasps didn’t make it, some of their sisters survived the winter by finding a warm place to sleep. They’ll start nests of their own next year, and the cycle will continue anew.

It’s sad, but that’s nature for you. It’s both beautiful and cruel…all at the same time.

At the end of every year, wasp societies collapse. The workers die, the queens hibernate, and new nests appear in the spring. It’s a simple story…but it’s not quite right. As always with insects, there’s more to the story.

There’s another layer of complication to how people tell the lifecycles of wasps, and the pictures above show a part of an interesting story that few folks know about.

Before they build their nests in the spring, the future queens gather for one last party.

The Timeline of Wasp Society Collapse

Wasp societies tend to collapse in late summer, usually around September in most of the areas where I’ve lived. Around this time most of the insects and flowers are just finishing up their end of the year lifecycles, but there’s still a little time for insects to still be active for a few months. In the locality of one of the pictures, it was right around the time of the first frost of the season.

So what are they doing?

After the wasps leave the nest, they go into hibernation. This happens in three stages, prehibernation, hibernation, and posthibernation. For the most part, entomologists talk mostly about hibernation…but these people have encountered these wasps during the prehibernation stage.

Prehibernation

Wasp dominance behavior towards nestmates. Picture A shows biting, picture B shows a ‘threat’ sort of behavior. Picture C shows mounting, while picture D shows a submissive post (on the left). Image Credit: Jandt et. al 2014

Prehibernation is a non-nesting social phase for this wasp. For people who aren’t constantly around wasps, it’s an extremely unusual phase because the wasps tend to be quite docile. This is because they have nothing to defend. There’s no nest, no offspring, and no reason to stand their ground. If encountered, and not directly threatened (e.g. by grabbing), they’ll just fly away as described by the observers above.

These pre-hibernation clusters can be extremely variable in size, from a handful of individuals to a couple of thousand of individuals. These are all mated wasps, each capable of making their own nest if given the chance. This stage of wasps is also unusual because they’re generally from a bunch of different colonies. In fact, there may even be multiple species. While Polistes dominula will out-compete rival species, they’re quite peaceful towards their competitors during this phase.

Even though they’re not in the nest, there’s still a lot of social interaction. There’s a group of wasps, the smaller and less dominant ones, who gather food for the more dominant members of this gathering. This is considered its own special social stage, analogous to a worker. Just like the workers, they typically don’t make it to the next spring.

The wasps which are destined to become foundresses, however, are doing something really interesting. They engage in fights, which they use to gauge their potential dominance in spring. These fights are typically consequnce free; they don’t result in any harm to any of the wasps. They also happen between wasps which aren’t likely to team up to form new colonies in spring. In fact, it’s almost identical to the fights that young mammals engage in before they strike out on their own.

In other words, in the eyes of some biologists who study wasps, these wasps are playing.

Hibernation

During hibernation, there’s not a whole lot that’s happening. As the season goes on, and as the weather grows colder, the wasps try to find a place that’s warm enough to survive. It’s a dangerous time, and a lot of these future foundresses die during the winter. However, enough survive to start new colonies in the spring.

Post-Hibernation

After hibernation, the new foundresses strike out to start new colonies. For the most part, it’s one to a colony. However, sometimes there are two foundresses. When there’s two, they’re usually sisters who left the same colony. In the invasive paper wasp Polistes dominula, only one out of three colonies aren’t sisters…and this is considered a high degree of relatedness.

If you’ve ever had a really bad roomate, you can kind of identify with what happens next. The paper wasp social structure is determined a lot by bullying. It starts out with passive-aggressive behaviors, where the two roomates stay at the opposite ends of the nest. The dominant foundress may eat the eggs of the subordinate, or make her go get food. After the first workers emerge, the interactions become a bit more aggressive. Unless, of course, there’s another nest with abandoned pupae nearby…which would give the other founding sister a chance to start her own colony with relatively little effort.

The Bottom Line

The pictures above show a time in the life of wasps which isn’t really talked about all that much, and isn’t well known outside of the world of entomologists. It’s also a really complicated stage; those helper wasps essentially become another caste of workers in a colony that’s composed of unrelated individuals…and this is extremely unusual among social insects. The wasps are also playing with one another, a behavior that’s not really considered among a group of insects that’s not entirely popular.

It wouldn’t be completely inaccurate to say that the pictures above are a literal wasp party…with friends going on food runs, and everyone playing games with one another.

Works Cited