Monday, September 1, 2014

Killer Wasps, Our Backyard Entertainment for August


Our neighbor called us on July 31.  "We have insects swarming in the back corner of our yard close to your lilac bush.  Will you come out and see if you know what it they are? I think they are wasps."

There were dozens of insects flying, sometimes landing on the grass briefly, sometimes flying about, mostly  four or five feet above the ground.  Sometimes they disappeared for a while into the arborvitae  hedge at the edge of our properties.  They did look like wasps but they ignored us, didn't seem at all interested that three humans were infringing on their chosen area.

"They're not aggressive. They act like the Cicada Killers  we had in the yard last year but they aren't big enough," Polly said.  We agreed.

"Go get that peanut butter jar Stephen was catching lightning bugs in," Tom told me.

I brought it but we were all leery of riling any wasp.  Nobody wanted to know what the insect was bad enough to risk being stung.

"Oh, I know...the butterfly nets," I said.  Sometimes being a well-equipped bug enthusiast has its rewards.

And that's how Polly caught this insect.



That evening her husband drove his riding mower through the area and the insects didn't bother him at all.

We  still weren't convinced the swarming insects were Cicada Killers (Specius speciosus)  because they were just too small. Finally, Tom typed "Cicada Killer" on the computer and via the world-wide web he confirmed that the coloring was right for a Cicada Killer.

Tom solved the problem of the size when he went down our driveway ramp on August 11.  There was a dead Cicada Killer on the ramp.  It was big like the ones we remembered from other years.  Mystery solved.  As in many  insect species, the Cicada Killer female is larger than the male.

Later I learned that the males hatch from the underground burrows before the females.

The female Cicada Killer digs a tunnel underground.  She digs chambers off the main tunnel.  Then she begins capturing Cicadas (Cicadidae) which she paralyzes and carries to her burrow one by one.  If she stuffs one cicada in the chamber and lays one egg on it, the egg develops into a larva which feeds on the paralyzed cicada.  It makes a pupa case and remains underground until the following summer.  When it emerges it is a male.  Eggs that will develop into females are provided with two or three cicadas.


We continued to watch the back corner.  On August 16, Stephen spotted a Cicada Killer carrying a cicada into a burrow.  We got a photo of the Cicada Killer reemerging.


We searched the area and found other burrows.  The holes were sometimes hard to see but the tiny balls of dirt which had been removed from the burrows were a giveaway.


I circled the hole with a blue line.  The tiny balls of dirt are circled with red.

On August 18 another neighbor brought over "a strange insect"she found on a young lilac sapling her son brought her.  It had a strange "thing on its back end".  The strange insect was a cicada emerging from its final molt.  We watched the insect pump up its wings and turn from white with tinges of green to the familiar dark colored insect we find every year about this time.  The cicada shell is on the bark above the cicada.


On August 26, Tom saw a Cicada walking slowly on our driveway.  Either, it had not yet completed its emergent changes or it was nearing the end of its life span.  Tom laid the dead female Cicada Killer beside the Cicada to get a photo of the comparative sizes of the two insects.


2 comments:

Far Side of Fifty said...

Interesting! I would have bet they were a Wasp or Hornet and the stings hurt so bad You guys are great insect detectives! :(

Pauline Persing said...

Cicada Killers are technically wasps but not an easily disturbed species. I still think Tom and Polly were brave (or foolish) to catch one in the butterfly net. Not too many daring bones in me.