Elm Sawfly and other Asian Giant Hornet Look-Alikes

The recent discovery of two additional, dead Asian giant hornets (AGH) has brought this invasive insect back in the news, but not with the buzz that surrounded the original report of 6 AGH in Washington and British Columbia back in early May.   

The ISU Plant & Insect Diagnostic Clinic and ISU Extension Entomology are ready and willing to help identify insects suspected of being AGH or any other insects that seem out of the ordinary. If a clear picture can be safely taken, send the image to insects@iastate.edu. Use extreme caution; photograph a suspect that is already dead or can be safely killed with spray or swatter.  If a picture is not available carefully record detailed observations such as size, shape and colors. 

The most common insect reported so far as a suspect AGH has been our native elm sawfly (Cimbex americana).  The elm sawfly is only 1 inch long (compared to up to 2 inches for AGH).  They are metallic blue with translucent, smoky-gray wings.  There is a prominent yellowish or white spot at the base of the wings. The abdomen varies from reddish brown to black.  Females have yellow spots along the sides of the abdomen.  The orange antennae are distinctly knobbed at the end.  Click here to see the University of Minnesota article on elm sawflies.

Sawfly wasps are non-stinging and harmless.  The immature stage of the elm sawfly is a large (2 1/4 inch long), wrinkly, yellowish-white larva with a prominent black stripe on the back.  They feed on leaves from elm, maple, willow and basswood.  Significant defoliation has been reported so monitor suspect trees in late June to August. 

Soon, the annual cicadas will start buzzing in trees from early afternoon to dusk.  That will be the signal to watch for our other, large, native wasp, the cicada killer (Sphecius speciosus).  Cicada killers are our largest wasp with a length of 1 1/4 to 1 5/8 inch.  The body is black with pale yellow stripes and spots.  The wings are translucent orange.  The cicada killer is a solitary wasp that provisions underground burrows with paralyzed cicadas that are consumed by the offspring.  See our online article for more information.

Finally, the bald-faced hornet (Dolichovespula maculata) is well-known for the papier-mache’ nests built in trees and on the sides of buildings.  The baldfaced hornet is a small wasp at 1/2 to 3/4 inch.  Bald-faced hornets ae black with white markings on the head, thorax, and abdomen.  Online article.  Images


The elm sawfly is a large wasp with a creamy-white spot between the smoky gray wings.
The elm sawlfy and other sawfly wasps cannot sting and are harmless.
Ccicada killer wasps are solitary and dig burrows in flower beds and along sidewalks and driveways
Cicada killer wasps have transulcent oragne wings and a black-and-white body.
Bald-faced hornets are moderately common and build paper-ache' nests in trees and on buildings.

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on June 5, 2020. The information contained within may not be the most current and accurate depending on when it is accessed.