Scary-looking, big black wasp alert

I’ve seen this insect several times earlier this summer, but never got close enough to photograph it.  Today it spent a lot of time in the swamp milkweed in the backyard garden, working the nectar out of the flowers.  It’s big, it flies fast and in unpredictable, random directions (meaning if you’re moving around taking photos, you might just wander into its path), and it looks like it could deliver a painful sting.

This s the Great Black Wasp, Sphex pennsylvanicus, a type of digger wasp.  Females measure about 1.5 inches, and have really long legs that dangle when they fly.  In the right light, its wings look almost blue-black.  It seems to be at least half again as large as a Yellow Jacket.

The Great Black Wasp is also known as the Cicada Killer, for its habit of stinging and paralyzing orthopteran insects (grasshoppers, cicadas, etc.) to provide food for their offspring.  The prey are paralyzed after being stung three times in head and abdomen and are then deposited in an underground nest. A single egg is laid on the underside of just one of the two to six prey items in each nest chamber.

Despite their fearsome features, the adult wasps are important pollinators, especially of milkweed species, and you can tell from the enlarged view below that they are carrying many of the yellow-gold pollen sacs (called pollinia) on their long legs.

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27 thoughts on “Scary-looking, big black wasp alert

    • Usually the Yellow Jackets don’t bother me, or I stay out of their way, but recently I have almost been stung when reaching in to pick raspberries and realizing the wasp is on the underside of the berry right near my fingers! Yikes!

      Sent from my iPad

  1. Dr. Chaplin, this is such great timing! We were at the park on Tuesday when all of a sudden we saw this HUGE yellow and black insect land in the sand and go into a burrow it had created along the sidewalk. I would say it was about 2 inches long and quite wide. So, being the biology-curious sort that I am, I immediately started Googling when I got home. From what I could find, all things pointed to this being a Cicada Killer Wasp. So, I felt okay with that answer until I saw your post…the wasps you photoed are all black with no visible striping. So, are there more than one species of giant cicada-killing wasps or did Google fail me? Also, on a side note, these wasps are thought to be a non-aggressive sort that only sting if provoked (squeezed or stepped on). The males are often seen jostling midair for territory, for the rights to mate with the local female, who is the only one of the pair with the ability to sting.

    • Yes, there is another species of Cicada Killer called the Great Golden Digger Wasp. It’s in the same genus and so looks much like the great black wasp, but with golden stripes. It also provisions its young with paralyzed prey in an underground nest, so that is probably what you saw. Did you have your camera with you?

      Sent from my iPad

      • Unfortunately, no. Plus, if I had, I don’t think the pictures would have turned out as I was leaving the area as fast as I could while still appearing to “keep my cool”. Now that I know they are generally docile, I will try to snap some pics if I see it again.

      • If you remember where that nest hole was, you could stake it out and wait for a really good photo. then send me a jpeg and I will post it on the blog as a guest entry.

        Sent from my iPad

      • I have no doubt I will be able to find the nest. I will see what I can get for you. :-)

  2. Pingback: the Great Golden Digger | Back Yard Biology

  3. Pingback: Another scary-looking, big, black wasp | Back Yard Biology

  4. Thank you so much for the pics and description as I have lived in Montana my whole life and have only seen the yellow stripped ones and have never really seen them digging.
    While in my yard this morning I saw exactly this,A big black one and it was stinging a large caterpillar in the head several times I sat and watched as it finally pulled the very large caterpillar down in the whole. I was very curious as to what type was inhabiting my yard so I looked it up and managed to stumble across your page not only with great pics but a description as well. So again Thank you!

  5. i didn’t hear anyone mention the POTENTIAL threat to humans by stinging from the black wasp.
    Are they aggressive to men?
    What is their nest TYPE?
    How to naturally deter them.
    Any aswers out there?
    e mail
    pcristantiello@gmail.com

    Thanks!

  6. I have these black looking wasps in my tree and there are probably about 25 to 30. They just stay in the tree, not alot of flying around but I am worried that they might sting us. Do I need to be worried about this and if so how do I get rid of them without killing my tree?

    • Dale, if they are hanging out together, they are probably not the wasps I wrote about in the blog, which are solitary. They might be bald-faced hornets (which are black and white, but might look black from a distance), which build a large paper, globe-shaped nest in a tree. Stay away from those — their sting is really painful. Don’t even think about removing their nest; get a professional to do it.

  7. Pingback: Nectar feast | Back Yard Biology

  8. Would these giant wasps be responsible for leaving mounds of sand beneath my stone wall?I thought maybe chipmunks were doing this, but today I saw the wasp come out of a crevice in the wall that had sand underneath it. Have to say they are quite lovely and never bother me when I’m close.

    • Perhaps so. They definitely dig burrows underground and would kick out the soil, as they do, leaving a mound of dirt around the entrance. The wasps will provision the burrow with paralyzed prey, enough to sustain the development of the larva through pupation.

      • We recently moved, and have noticed several of these wasps inside of our house, all at different times. Do we need to worry? How would I go about finding the burrow? I’m freaking out that they may be living IN our walls/house.

      • Nope, they should not bother you in the house/walls because they definitely nest in the ground. That is a relatively short period (nesting) and they are probably gathering food to provision their larvae with. No worries. Where do you live that they are active now?

      • We’re in Southern Indiana, Georgetown, to be exact. It was 70 degrees yesterday, but the temp has since fallen to the 30′s, so I imagine they won’t be a problem for the next few months.

  9. Hello, I recently found a dead and well kept corpse of a large black wasp. It measured two inches from stem to stern. The largest black wasp I have ever seen, it was in my home, stuck on a sky light screen. I have photos. Can you tell me anything about this specimen. I will send you photos if you like

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