What insect starts life like a butterfly or moth, but emerges from its cocoon looking like a wasp? If you’re like me a few months ago, maybe you’ve never heard of them before, but the mystery morpher is a sawfly.
Sawflies are in the same order as wasps and bees: Hymenoptera. Adults resemble wasps without the thin, “wasp” waists. There were dozens of the orange-abdomen type flying around unfurling ferns at Mt. Pisgah last week. I believe they’re in the Strongylogaster genus, which lays eggs in ferns, and indeed I think that’s what the female in the picture is doing. In fact, these insects are called sawflies because the females have a saw—it honestly folds out like a Swiss-army knife tool—to slice open stems and leaves so it can deposit eggs there.
The longer, thinner sawfly is a stem sawfly in the Cephidae family, and it illustrates another butterfly-like trait of these fascinating fliers: The antennae are enlarged at the ends. Some sawflies have branched antennae, some can be feathery, and some have antennae that split into long pairs, making two shapes that look like tuning forks!
Like a lot of wasps and bees, sawflies can be particular about their food and breeding grounds. Name a tree or plant, and there’s probably a sawfly associated with it. Their suborder name, Symphyta, illustrates this trait (sym = together, phyta = plant). The Cephidae sawflies were easy to spot on the yellow cinquefoil, and they only showed up in the meter-square area where the flowers were blooming.
Sawfly larvae have interesting traits of their own. Keep your eyes open for groups of caterpillars rearing up in unison, forming “S” shapes. If I see any, I’ll write about them in a future column.
Well-done intro webpage from Missouri Botanical Garden: http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Insect%20Orders/Hymenoptera-Sawflies.pdf. Accessed 5/5/21.
Refreshingly pro-insect hemlock sawfly article: https://www.kfsk.org/2018/08/17/southeast-alaskas-forest-yellows-from-an-insect-outbreak/. Accessed 5/5/21.