When BWWs, which are in the Common sawfly family Tenthredinidae, are found south of the Mason-Dixon Line, it’s mainly in connection with black walnut trees, but the bulk of their range is the northeastern quadrant of North America-not coincidentally, the range of the butternut tree. Larval defense strategies include communal feeding (potential predators have trouble figuring out where one larva stops and the next one starts) and spitting vile liquids from their mouths. One source said that many of the plants that sawflies prefer are chemically defended, which seems to bother the sawflies not at all. Sawfly larvae are fussy eaters, with many species tied to just a few host plants, and some larvae are considered pests.

Sawflies lack the “wasp waist” of other Hymenopterans, and although their larvae are often mistaken for caterpillars, the legs are different. The females’ toothed ovipositor gives them their name. Sawflies-sometimes called “wood wasps,” a common name they share with a few other primitive wasps-are harmless members of the wasp order, Hymenoptera. It’s a Butternut woolyworm ( Eriocampa juglandis).

Then she looked more closely at a larva and suspected that it might be a sawfly, and Google became more accommodating. The BugLady, who is key-word-challenged, feels their pain. It was fun reading accounts in which other authors experienced similar confusion, several describing the joys of Googling “fuzzy white worm,” and other descriptors. Wooly alder and wooly beech aphids cover themselves with waxy filaments, and so do the nymphs of some planthoppers (and she had photographed what she thought was a feathery planthopper on her own walnuts last year), but worms? Anyway, two weeks later, she was staring at some of these mystery worms in person. When she got a query recently about the identity of a three-quarter-inch “worm” that had feathery tufts and hung out on the bottom sides of leaves, it didn’t ring any bells. Lots of BOTW pictures are also floating around in Google Images, which results in a steady trickle of correspondence both national and international (the BugLady cheerfully told the folks at a Field Station in India that solving their problem of small aquatic worms and other invertebrates in their tap water was way beyond her pay grade). The BugLady keeps running into herself on-line as she does research, which is scary-makes her think that she ought to know what she’s talking about.

Download butternut woolly worm