Saturday, August 10, 2013

Cicada Killer

Larry Wegmann
Larry Wegmann emailed me this picture of a large wasp-like insect he photographed in his garden.  Here is his description.
"This guy has found it's home among our impatiens in our backyard. It protects this patch from other intruding wasps.  I noticed in these pictures that this is probably a male wasp. If its his girlfriend he is chasing away from his nectar source, he needs a lesson in vinegar vs. honey. By the way I took these with my Nikon D90 with a 300 mm + 1.4 tele-extender = 420 mm lens.  I wish this guy would tolerate me getting close with the Pentax with high speed video.  He is very alert to my presence."
Larry had already identified it as a cicada killer, Sphecius speciousThe largest wasp in North America, it is fearsome in appearance but in reality it is more of a pussy cat.  They emerge from the overwinter cocoons in mid-July.  The female, twice the size of the male, uses her stinger to paralyze cicada and won't sting humans in self defense unless roughly handled.
Larry Wegmann
S. specious  with paralyzed cicada- Wikimedia
Following fertilization, the female cruises around, finding a suitable site to lay her eggs, then digs a burrow with one or more side chambers.  Next she patrols nearby trees until she find a cicada.  Once it is paralyzed, she struggles with the flight to carry it back to the burrow.  As the cicada will weigh twice her body weight, she may need a few rest stops along the way.  Once she has worked it into the chamber she lays her egg on it and closes the cell with dirt.  If it is a female egg, the cell usually will be provisioned with two cicadas as the larger female will require more resources to grow.

Velvet "Ant"- The Ant that Ain't
The egg will hatch in a few days and the larva will develop over 20 days and overwinter as a pupa in a cocoon.  The adults, their job complete, will die off over the fall, none surviving by the next year.  Meanwhile the larva is vulnerable to the same risk as its paralyzed cicada host.  Velvet ants, a.k.a. cow killers, Dasymutilla occidentalis, are actually furry flightless wasps.  They specialize in solitary ground nesting bumblebees and wasps. finding their nests and laying their eggs on the cicada killer larva for their own larva to feed upon.  From the cicada's point of view, this must seem like poetic justice.

Cicada Killer- Shelly Cox at MOBugs
Meanwhile the male cicada killer patrols looking for nectar and more females.  It will select a territory and defend it, flying up to inspect anything that comes near and fighting off other males.  Smaller than the female, they still are frightening but a hollow threat as they lack stingers.  The males are more likely to buzz us humans to be sure we aren't available females.  Larry's description above suggests his was a male.

Like all other animals, the cicada killer is a mixed blessing.  They are welcomed by our trees as they reduce the numbers of cicadas, a forest parasite.  The annual cicada likely don't see it that way.  They don't have any effect on 13 and 17 year cicadas which emerge in May and June, dying off before the cicada killers arrive.  With our neatly mowed lawns and loose flower beds providing both nectar and easy digging, it is no wonder that S. specious has learned to love the suburbs.  Keep your eyes open and you too may be able to follow this gift of nature.

Dick Walton's Natural History Services page has a great 4 minute video of cicada killers.
Extensive information on S. specious is available at Professor Chuck Holiday's page at Layfette College




2 comments:

  1. I was fascinated by the Cicada Killer Bee's stinger and how it can penetrate the hard exoskeleton of the cicada. So I caught one and handled it with gloves to get a better look. It has a wedge shaped stinger of about 1 mm. Unfortunately for me, the bee found a hole in my glove and stung me, it took about a month for full feeling to come back in my finger. Jay Barber

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    1. Simon & Schuster put out a 1981 book on insects, the cicada killer is profiled, "the female is said to have one of the most severe sting of any insect." There are academics insisting the sting is mild. Sorry, but I must say they are intentionally lying, the question is why. They know if a sting is taken immediately after the CK has discharged venom into a cicada, the sting will have a 90% or more reduction in impact, giving the false view that the sting is mild. Master Beekeeper site says it may hurt as long as a week. Only point I agree with the vaunted "professor" is these wasps aren't very aggressive. Nature Magazine circa 1928 also said it can "sting severely." Can university professors be horribly wrong? You bet. Sure they took stings when the venom sac was depleted and they knew it was depleted, even a rattlesnake bite could be made tolerable this way.

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