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Archive for September, 2012

Occasionally, I’ve come across a cicada lying on the ground, motionless, but seemingly alive and wondered how it got that way. Earlier this summer, I found out.

Cicada Tibicen abandoned by Cicada Killer

Cicada–motionless, but still alive?

In late July, I was standing on my patio when I spotted a wasp-like insect that was about 1 ½ to 2 inches (38 to 51 mm) long. Its body was brownish-black with yellow markings, and it had shiny, rust-orange wings and legs. It flew slowly back and forth just above the patio’s surface and then entered what appeared to be a freshly excavated hole between two patio stones.

I did a Google search on “large burrowing wasp”, and the first hit was a Wikipedia entry on Sphecius speciosus, a large digger wasp commonly known as the Eastern Cicada Killer. The description and photos matched the insect that I had seen.

Cicada Killers, true to their name, hunt and capture annual cicadas to feed their larvae. I usually start to hear the loud, raspy songs of male cicadas in early July. I learned that Cicada Killers emerge soon after. After mating, female Cicada Killers excavate burrows that will hold both their larvae and the cicadas that the larvae will feed on. They locate their burrows in well-drained soils, often in patios and sidewalks, and always near large deciduous trees where cicadas feed on sap.

Although the Cicada Killers are large and somewhat frightening looking, they actually are docile around people. The males don’t have stingers, and the females will deliver a mild sting only if handled roughly.

Excavating the burrow

Cicada killer Sphecius speciosus excavating

Cicada Killer pushes soil with her rear legs

The next day, I watched a female Cicada Killer excavate a new burrow beneath the patio. She entered a hole in the sandy soil between the patio stones and, after several minutes, backed out of the hole, pushing the soil with her spurred rear legs. She looked like a mini bulldozer working in reverse, and she amassed a quantity of excavated soil many times larger than herself. I read that Cicada Killer burrows can be up to three feet long and extend two feet below the surface. I also confirmed what I had read about their docility—I approached the female closely but she was oblivious to my presence.

Cicada killer Sphecius speciosus excavation

That’s a lot of soil to move

The hunt for cicadas

When her burrow is complete, the female Cicada Killer begins hunting. She hunts by sight and, after capturing a cicada, she uses her stinger to inject it with venom that both paralyzes and preserves the cicada, but does not kill it. Keeping the cicada alive keeps it in a fresh, edible condition for longer than if it were dead. The Cicada Killer flies from the tree back to the burrow with her prey—no easy feat, since the cicada is about twice the weight of its killer. After the larvae hatch, they begin to feed upon the paralyzed, still living cicadas that their mother has provided.

Female cicada killer sphecius speciosus hovers

Female Cicada Killer hovers over burrow entrance

Mishaps happen

Cicada Killers sometimes accidentally drop their heavy prey when flying to the burrow. Cicada Killers aren’t strong enough to take flight from ground level with a cicada in tow, so they often abandon it. They also may abandon their prey if they mistakenly land too far from their burrow entrance. The motionless cicadas that I’ve found were likely abandoned by Cicada Killers. Unfortunately for them, the paralyzed cicadas are easy prey for ants and birds.

Looking forward to next year’s show

During the several days that I saw the female Cicada Killer flying about the patio, I never witnessed her toting a captured cicada back to her burrow. Hopefully, she did so unseen, so that I can have a better chance of watching these fascinating insects again next year.

For more information

Professor Chuck Holliday of Lafayette College in Pennsylvania has an excellent website on the biology of Cicada Killer Wasps.

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