Cicada-killer wasps

Posted on July 20th, 2012 by

cicada-killer wasp

This relatively harmless cicada-killer wasp has a burrow in one of the beds of the Linnaeus Annual Garden. This photo was taken by Arboretum visitor Chris Hayes.

Most gardeners have had the occasional encounter with a wasp.  Whether it’s a confrontation with a paper wasp or an unfortunate misunderstanding with a hornet, most of us are personally familiar with the havoc and anxiety that a wasp can create.

Then there are the cicada-killer wasps.  When it comes to panic-inducing capabilities, the cicada-killer (pronounced si-KAY-duh – killer) is in a class by itself.  We’ve noticed at least one such wasp this summer hanging out in our large annual garden at the Arboretum.

Without a doubt, their most intimidating feature is their size, as a large cicada-killer wasp may be nearly two inches in length.  They sound nasty too.  To generate enough force to keep their massive bodies airborne, their powerful wings hum menacingly as they fly.  In flight, they skim low over lawns and gardens as if searching for small neighborhood children to carry off.

Yes, few things will send you updating your life insurance policy and tying lead weights to your children like watching a wasp the size of a Toyota Corolla patrol your yard (these things are the real life equivalent of those flying monkeys on the Wizard of Oz).

But, as with most things in this world, our fears are largely unjustified.  Despite their frighteningly large size, humans have little to fear from cicada-killers.  As their name implies, they are not after us, but are after insects known as cicadas.

Cicadas, of course, are those noisy insects that make the loud buzzing sound high in the trees in the hot part of summer.  A cicada is about two inches long with a green and black coloration and a pair of large wide-set alien-like eyes.

Many people have never seen a cicada, since they are only present for a small portion of the summer and are either found high in the trees, or deep underground.  A cicada lives nearly all of its life by itself underground sucking on tree roots.  A cicada nymph can stay underground for as many as 17 years before emerging in the hot part of summer to find a mate and lay eggs to continue the life cycle.

At least one insect species, the cicada-killer wasp, has evolved to take advantage of all those cicadas emerging at the same time each summer.  A cicada-killer wasp uses its stinger to paralyze and subdue a newly-emerged cicada to be used for food.  The wasp does not eat the cicada, but rather uses it to feed its young.

In fact, it is only the female wasps that have stingers.  Male wasps, while highly territorial, do not have stingers at all and appear to be useful only for the one thing that males of most species appear to be useful for.

Both the male and female wasps feed harmlessly on flower nectar and pollen.  Despite the stinger, even the female wasp is relatively harmless, as she prefers to use her stinger primarily for obtaining prey and rarely for defending herself.

After stinging and paralyzing its cicada victim, the female wasp will straddle the immobilized cicada and either drag or fly the victim to the entrance of its nest burrow.

Nest burrows are dug into the ground by the mother in sunny, sparsely vegetated areas of light, well-drained soil.  The nest opening is only about the size of a quarter, but extends six to ten inches deep and terminates with a few cells, each one containing an egg laid in midsummer.

After bringing a cicada to the nest, the mother wasp drags the lifeless cicada down the tunnel and leaves it in a nest cell next to a developing egg.  The mother wasp will usually leave two or three cicadas for each egg in the nest.

Upon hatching, the young wasp larvae feed on the cicada carcass until they become full-size larvae at which point they wrap themselves in a leathery, brown cocoon for the winter.

After the next year’s summer sun warms the soil sufficiently, the young wasp larva pupate and emerge from the nest to feed on flowers until it is time to mate, lay eggs, and await the emergence of that year’s crop of cicadas.

 


One Comment

  1. Connexion says:

    Ciao all-When the yellowjackets are in nomral populations, they don’t bother me as much as they used to. I used to have a serious phobia of them, stemming from the time as a toddler, I unknowingly stuck my entire arm into a nest. The entrance was a knothole in someone’s deck. We have a pear tree and they nomrally will buzz around the fallen fruit. I’ve even gotten to the point where I can pick the fruit up even when they’re buzzing around it, a huge step for me.However, this year, it’s a different story. They’ve built nests in 2 places on either side of our garage, making it nearly impossible for me to get the car out or even open the door. As a full-time gardener, I couldn’t deal with that kind of impact into my work schedule so we ended up using an exterminator who uses some kind of benign soapy water spray. They’re still there, having eaten through the crack filler Duane put in there, attempting to wall up the nest, but their populations are now much lower so I can walk around the side of the house and open the garage safely.I figure we have a few more weeks of their nonsense before their food supply dwindles and so do their numbers.