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Cicada killer wasps come every summer to feed on the dog days cicada, a bug that emerges in July and August.
Cicada killers dig a burrow in which to lay eggs on the cicadas they capture and drag into the den.
A cicada killer is among the largest wasps.
A cicada killer is among the largest wasps.
A cicada killer wasp clings to netting with its kill. The large wasps appear every summer in eastern North America, their ermgernce timed with the arrival of the dog days cicada.
Sunday, July 28, 2013
If looks could kill, an insect buzzing around these parts this summer would be a serious assassin.
It’s a wasp, and a big one, with a fat body about an inch-and-a-half long.
But while the critter can appear quite menacing — especially territorial males — its threat to humans is minimal.
Its threat to another insect is quite serious, however.
The insect is the cicada killer, and its name is well earned.
Cicada killers haven’t appeared because of the well publicized hatch of 17-year periodical cicadas experienced across much of Virginia earlier this summer.
The wasps come every summer because they feed on the dog days cicada, a bug that emerges each summer in July and August.
As the manager of the Insect Identification Lab at Virginia Tech, Eric Day is accustomed to getting questions about cicada killer wasps.
Day does his best to explain the insects.
Many bees and wasps are social insects, Day explains, with groups consisting of a queen and workers.
When threatened, social wasps and bees are willing to sacrifice workers to protect the queen. That’s why stumbling into a hornet or wasp nest can result in painful stings.
Cicada killers are different.
“Each one is a solitary wasp,” he said.
Their primary goal is reproduction, not protection.
“They rarely sting,” Day said of the insects, of which only the females are able to sting. “But they have kind of an aggressive behavior when you’re around them.”
According to an FAQ on cicada killers put together by the University of Kentucky’s College of Food, Agriculture and Environment, some animals can have painful encounters with cicada killers.
“Some dogs and cats may catch cicada killers but usually only once,” the FAQ reads. “Those that pick females probably will be stung, remember it, and associate the experience with the buzzing sound and warning colors.”
The stings can be dangerous to people and animals that react severely to bee and wasp venom, in which case medical attention can be required.
Female cicada killers excavate a den, digging a half-inch diameter entrance hole. A tunnel system can be 12 inches below the surface and up to 6 feet long with side chambers to harbor individual cicadas.
Cicada killers prefer sandy, lighter, well drained soil because digging is easier.
Then the female flies off to hunt for a cicada.
In general, where you have buzzing dog days cicadas, you will have cicada killer wasps.
After locating a cicada, the wasp attacks, stinging and paralyzing its victim.
Then comes the tough part: getting the large cicada, which can weigh two or three times as much as the wasp, back to the den.
“They are not strong enough fliers to fly more than a couple hundred feet” with their catch, Day said.
On their return flight, cicada killers gradually lose altitude until they hit the ground.
Then they will climb up something, typically a tree, to regain altitude before taking off again.
Returning to the excavated den can take several separate flights.
Once at the den, the cicada killer drags the helpless cicada into its burrow, then into a side chamber. After laying an egg on the cicada, the wasp seals up the entrance to the side chamber.
A den system can contain many cicadas and cicada killer eggs.
When the egg hatches, typically within just a few days, the larvae has a big meal right on hand.
“And it’s fresh,” Day said of the cicada, which is likely still alive.
The larvae grows into a grub. As the cool weather of fall arrives, the grub spins a silken shell and enters a pupal stage for the winter.
After hatching the next summer, the cicada killer emerges from the den and the cycle starts anew.
Day said many people who have encountered cicada killers leave the insects alone when they better understand the insects’ life cycle.
But he also understands that some people will still have the desire to eliminate the wasps.
“If conditions are right, you can find a lot in the same place,” he said. “You do get people who want to control them.”
Legal, commercially available insecticides can be used to target the dens.
“But they are very hard to control” on a large scale, Day said.
For those who are willing to let the cicada killers go about their business, they may get lucky and get to see the unique hunters in action.
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