Common Dogwood Sawfly

2014 September 3

On August 13, 2013, Sandy found several of these sawfly larvae busily defoliating a dogwood bush alongside the trail behind our house.

Quick leg check, count the prolegs: yep, eight pairs. It’s a sawfly, all right.

The white color is due to a powdery wax that it secreted on its skin. The actual color on top is obscured, although it probably would have been some shade of yellow-green.

The head is pretty uniform black, aside from the wax dust, which distinguishes it from some otherwise similar sawfly larvae that I posted a couple of months ago.

and the underside (which is free of the obscuring wax) is yellow to light orange.

The best ID feature is the foodplant, since there are several other kinds of sawfly with that same waxy bloom, but not many that eat dogwood. I think it is a half-grown Macremphytus testaceus. If we’d found it a bit later in its development, it would have lost the wax dust, and been yellow-orange all over, with black spots.

I think that the dogwood that we have out back is the Northern Swamp Dogwood, Cornus racemosa. It has white fruits growing on red stems, and I see multiple references saying that birds eat the fruit. No mention of people eating the fruit, though. Since there are no cautions about them being toxic, I expect that they are edible in the not-killing-you sense, but probably not very tasty to humans (or maybe to mammals in general).

2 Responses
  1. Carole permalink
    September 3, 2014

    Have read that sawflies are a favorite of bluebirds, but don’t know if they would be put off by the waxy powder.

  2. September 5, 2014

    Well, we do have a few bluebirds around, and *something* seems to be eating the sawfly larvae – their numbers start fairly high every year, and then drop off abruptly.

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