What's That Bug? does not endorse extermination

What are these?!
Location: South Carolina
June 19, 2011 2:42 pm
My daughter and I found these on our back porch in SC in the summertime. We found three yellow ones and one brown one…
Signature: Rebekah

Giant Mayfly subimago

Dear Rebekah,
All of your photos are of Mayflies in the order Ephemeroptera, and we believe they are Giant Mayflies, or Golden Mayflies, or Burrowing Mayflies in the genus
Hexagenia, based on images posted to BugGuideBugGuide notes:  “Very large mayflies. Usually pale golden yellow at least when freshly emerged, i.e., subimago. Several species dark with bold striped pattern as mature imagos. Wings not uniformly dark, as are some other genera of this family. Pale brown band across abdomen. Antennae, legs, and tails yellow. (Photographs show either pale golden mayflies–probably subimagos, or very dark individuals, full imagoes?)”  Mayflies are unique among insects in that they molt twice as adults.  Daniel Marlos in his book, The Curious World of Bugs, writes:  “Shortly after emerging from the water in preparation for becoming an adult, the naiad, or aquatic nymph, molts and assumes its winged form.  This is known as the subimago because within a few hours, it will molt again, shedding even the covering of its wings, at which point it becomes a full adult, or imago.”  We are inclined to believe that your yellow individuals are sumimagos, and the brown individual is an imago or mature adult.

Giant Mayfly imago

What's That Bug? does not endorse extermination
Location: South Carolina

2 Responses to Mayflies


    in around 1978-1982 approximately, in brooklyn, new york. i witnessed some flying insects with long stingers boring holes in a large (lightning damaged) tree in the front of my neighbors house, i was told that they were called mayflys. i was between the ages of 8-12 yrs old and didn’t do much more research regarding it assuming the information i received was correct. some years later i was in long island, new york climbing on the underside of some bleachers , beside a football field and i was stung by two of these same insects. upon closer inspection and extraction of the stinger, i noticed it had a three pronged stinger, one part was hard and sharp the other two parts were softer and intertwined with the main piercing stinger. i was telling someone about it and they said it couldn’t be a mayfly. so i went online to do more research, to find out if it was or wasn’t and what it could be. now i have read that mayflys don’t sting and it seems only male giant mayflys could fit the description of what stung me. i do not have images and in brooklyn there was no lake or pond for mayflys to have bred so close to the tree i witnessed them boring holes into. Which based on what i have read, could rule out most mayfly species, Also, I have not seen these insects again, in the last 25 years or more, i have no images but to my recollection they bore holes that were about 1/4 in diameter and at least deep enough that you couldn’t see how deep they were. the stingers were a minimum of 3 inches long, now i may be remembering a slightly more exaggerated stinger approaching 4-5 inches, but that can just be faulty memory or trauma induced memory. regardless, they were the same insects boring holes in the tree and made so many holes in fact the tree eventually collapsed and they most certainly stung me with little provocation. does anyone have any idea what these flying, boring , stinging insects were?

    • bugman says:

      Your entire description is a perfect fit to a Stump Stabber, a Giant Ichneumon in the genus Megarhyssa. The only thing that does not fit is your account of being stung. While we imagine that since the ovipositor can bore into wood, it is possible to be stung, it is our understanding that Stump Stabbers do not sting. According to Icheumon Wasps by Lloyd Eighme on Skagit.wsu: “It might frighten you, but if you could watch it long enough you would be amazed at what it does. It lands on the bark of a tree and crawls up and down, tapping with its long antennae, obviously searching for something. Eventually it finds the spot it is looking for and begins to drill into the bark with its long needle-like ovipositor. It has detected the larva of a horntail wasp chewing its tunnel in the wood an inch or more below the surface of the bark. The ovipositor is made up of three stiff threads, hardened by minerals, that fit together with a groove in the center. Vibrating those sharppointed threads forces them into the bark and sapwood of the tree to contact the horntail grub in its tunnel. An egg is forced down the ovipositor to parasitize the grub. If the ichneumon parasite larva killed its host, they would both die, trapped in the solid wood which the parasite is unable to chew. It only feeds on the nonvital organs like the fat body until its host has nearly completed its life cycle and has chewed its way out near the surface of the bark. Then it kills and consumes its host grub and completes its own life cycle to emerge as another giant ichneumon wasp in the genus Megarhyssa (mega=large; rhyssa=tail) to start over again. You can see both Megarhyssa and its horntail wasp host in the MG collection.
      People often ask if the ichneumon wasps will sting them with their needle-like ovipositors. The wasps are interested only in laying eggs in caterpillars or other insects, but if you handle a live one it may try to sting you in self-defense. Small ones could not likely penetrate your skin, but larger ones might be able to.”

Leave a Reply

Your email address will not be published. Required fields are marked *