Subject:  mystery hoverfly
Geographic location of the bug:  Mt St Helens, Washington, USA
Date: 07/11/2019
Time: 08:08 PM EDT
Your letter to the bugman:  Seen June 30, 2019. It’s with body was slightly over an inch (2.5-3 cm) long. Seen at Coldwater Lake, Mt St Helens National Volcanic Monument. A friend thought it might be a species of Tachinid Fly. I would be interested to know if anyone recognizes it.
How you want your letter signed:  Linda Severson

Sawfly: Trichiosoma triangulum

Dear Linda,
This is not a Hover Fly nor any other True Fly.  Flies have a single pair of wings and your insect has two pairs of wings.  The clubbed antennae characterizes it as a Sawfly, a non-stinging relative of stinging Bees and Wasps.  We believe we have identified it as
Trichiosoma triangulum thanks to images on BugGuide.  According to BugGuide:  “Larvae feed on leaves of alders (Alnus), ash (Fraxinus), poplars (Populus), willows (Salix), cherries (Prunus).”

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