Great black wasp

This beautiful creature photographed by Andrew Hogg is not actually a “blue wasp” but a great black wasp, Sphex pensylvanicus. According to John Ascher of BugGuide.net, only the wings are blue. It belongs to the family Sphecidae, the thread-waisted wasps, and if you look carefully at the photo, you can see the very thin connection (petiole) between thorax and abdomen.

This is a solitary, ground-nesting wasp. The adults feed on nectar and are especially fond of Asclepias (milkweed), right where Andrew found this one. The adult female feeds grasshoppers and katydids to her young. She finds a suitable meal, paralyzes it with three stings, and then brings it back to the nest. The prey doesn’t die right away, but can remain paralyzed for weeks, assuring fresh meat when the larval wasps need it. Gruesome, eh?

These wasps are found throughout North America, including Canada, Mexico, and most of the US except the Pacific Northwest. They are considered important pollinators of Asclepias and some other plants including wild carrot, snake root, and white sweet clover. They can be seen in fields and meadows on mid- to late-summer days when grasshoppers are plentiful.

The males, which are smaller than females, are known to fight each other for territory and engage in activities such as biting and grappling with their spiny legs.



A great black wasp nectaring on milkweed. Only the wings are blue. © Andrew Hogg.


  • Aren’t they gorgeous?! I saw one in August in Haliburton, Ontario, Canada. Very striking…do not remember seeing these as a child when I lived there. This one was feeding on an hydrangea.

    • If you are asking if they sting, yes, they sting. But are they dangerous? They are solitary ground-dwellers, which means one wasp lives in a hole in the ground by herself. How dangerous can that be? It’s a waste of life to be afraid of life.

  • Yesterday a female black wasp stung a small Bird several times in my yard. The bird died instantly. I don’t think she mistook it for a grasshopper or katydid. It was 3-4 inches long and Big !
    I am guessing the female is dangerous if aggravated.

  • Are these wasps harmful for monarch butterflies and milkweed? Since they started coming to my backyard, the monarch butterflies are not visiting anymore. What is happening? Thanks.

  • Veronica, I have looked up online info regarding the giant black wasp. She lays her eggs on caterpillars and bugs as a host for the larva as they grow. Yellow wasps lay their eggs on tomato worms.

    I have monarchs fly around my yard, but I can no longer find the caterpillars I had … and I cannot find any cccoons.

  • I have a swarm of some sort of wasps on my porch every night for the last week and they look very similar to the Great Black Wasp, but everywhere I look it says they are solitary. They only show up at night and they are not building a nest. they all look to be sleeping. I was hoping to find out how to identify them, because if they aren’t dangerous, I don’t want to hurt them, but there are dozens of them.

    • Carl,

      Solitary wasps can gather together, just like a bunch of bachelors can go to a bar. Sign up for an account on iNaturalist and submit pictures. Someone there will identify your wasps.

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