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What is this?!
This mysterious mass of larvae wrapped in silk was discovered last week in Woodland Park. At first glance, it might look like a frightening invasive species—but bug lovers know that even the strangest-looking larvae can have a fascinating story.
Not wanting to jump to conclusions, we opened the case of the mysterious Woodland Park larvae.
First suspect: tent caterpillars. No—they’re most active in spring.
Fall webworms? No—their larvae are pale with black spots.
Had we stumbled onto an X-File? Maybe.
Enter Wisconsin’s Bug Guy, Patrick “PJ” Liesch, director of the UW–Madison Insect Diagnostic Lab. He identified these unusual suspects: cherry webspinning sawflies.
Case closed!
Cherry webspinning sawflies (Neurotoma edwardsi) lay their eggs on cherry trees. After hatching, the larvae feed on the leaves inside communal silk webs filled with folded leaves and droppings, also known as frass. They take turns eating and spinning, expanding the web whenever they need access to fresh leaves.
After about three weeks, the mature larvae drop to the ground and spend the winter underground as pupae. The adults emerge in spring, and the cycle begins again.
Although feeding by cherry webspinning sawfly larvae can look alarming, it rarely affects the tree’s overall health. These native insects are simply living their bug lives!
Video: Stephanie Briand, Aldo Leopold Nature Center
#PhenologyFriday #WebspinningSawflies #WIEnviroEd #NatureIsEverywhere #NatureIsForEveryone #EveryBodyOutside UW-Madison Department of Entomology
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