Green Sawfly

2021 May 23

This sawfly came to our porch light on June 9, 2020.


Sawflies are broadly related to wasps, but they don’t have stingers. Their caterpillars generally eat leaves the way moth caterpillars do, and the adults generally look like this with fairly stocky bodies and kind of wasp-like heads.


There are lots of kinds of sawflies, mainly differing in what plants they eat. Without knowing that, it can be hard to identify a random adult like this. The green color would seem to be fairly distinctive, and I think it is one of the sawflies in the genus Nemantus. These are commonly known as the “willow sawflies”, even though they don’t all eat willow leaves as larvae.

The issue in identifying this particular one further, is that BugGuide says there are 60 species known in this genus in North America, but they only have pictures of 11. Which means that there are excellent odds that this particular species is not one of them that they have pictures of.

And, once again, the big issue in identification becomes the need for someone to care specifically about them. If this was a crop pest it would be easy because there would be numerous papers on how to control them. If it was unusually beautiful or interestingly weird, then lots of people would be taking pictures and posting them. But, since it is just a generally pudgy, green, nondescript sort of thing that generally minds its own business, it is left to people like me to actually catalog their existence.

4 Responses
  1. Carole permalink
    May 23, 2021

    I’ve read sawfly larvae are a favorite of bluebirds.

  2. May 23, 2021

    Yes, I expect bluebirds do love them. My daughter’s chickens certainly are eager to chow down on sawfly larvae.

  3. May 29, 2021

    If they don’t have an objective differentiation process, how do they know there are 60 different kinds? If your life depended on accurate identification, could the insect authoritative sources do it?

  4. June 1, 2021

    KT: The actual taxonomists will examine the insect in a lot more detail than I am set up to do, and the insect generally doesn’t survive the process. They will measure the pattern of wing venation, examine the genitalia, look at the body morphology at high magnification (particularly the legs and antennae), and these days will also commonly perform a DNA analysis. And full ID keys are published in the professional entomology journals. So yes, equipped with a good microscope and an ID key, an actual entomologist could either get it identified to species pretty quickly, or propose it as a new species. And the DNA analysis can confirm that.

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