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Elm sawfly just a curiosity

Male elm sawfly. 
Photo:  Steve Katovich,
People across Minnesota have been sighting large, wasp-like insects recently. Fortunately, elm sawflies are harmless but if you have not seen them before, you would certainly be curious about them.

How to identify

Elm sawflies are very distinctive in appearance.  They are stout and about 3/4 inch long.  They have a dark colored head and thorax (the middle section behind the head) with orange antennae.

Males have a reddish abdomen while females have a black and cream striped abdomen. However, both sexes have a whitish to yellowish spot on the abdomen near the thorax and they both have smoky colored wings.

You can see elm sawfly adults in May and June. They are associated with different hardwood trees, including willow, poplar, maple and elm, where they lay eggs. They may also be found visiting flowers.

Elm sawfly larva.  Photo: Herbert A. 'Joe' Pase III,
Texas A&M Forest Service,

The larvae are big....

Later in the year, the larvae themselves are also a curiosity.  They are the largest sawfly in North America, growing to 1 ½ to 2 inches long. Their body is light yellow to light green in color, sometimes even pink.

They have a black stripe along its back and black dots on the base of each segment. They commonly coil into a ball to protect themselves.

Can they do damage?

The larvae are active from July to September. Despite their size, they are not a pest of trees and can be ignored when found.

For more information and images, see BugGuide.

Author: Jeff Hahn, Extension Entomologist

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