Butternut Woollyworm

 

Along our lane I came across a little walnut with badly chewed leaves and this on a petiole.  I found two others on the underside of leaf remnants, all immobile until I annoyed them.  This is a butternut woolyworm, Eriocampa juglandis.  It is a sawfly, the combined name signalling that it isn't really a "fly."  It is actually a member of the wasp family only with a thicker waist.

 

 

In a closeup side view you can make out the legs on the thorax.  The larva is covered with a white material thought to deter parasitoids and predators and it certainly isn't very appetizing to me. I could find white patches of fluff covering exuviae as they molted but it clings onto the larva unless scrapped away as you see in this video as I annoyed it into action.

 

BWW larva and exuviae

Walnut sphinx moth - Shelly Robertson

 

 

 

The BWW caterpillar-like larvae have a voracious appetite but are picky eaters, only feeding on walnut and hickory.  Walnuts produce a chemical called juglone that is allelopathic and inhibits a lot of competing plants in the vicinity.  It is also a natural insecticide, warding off predators.  Species like the BBW and walnut sphinx moth can detoxify juglone, converting it into a harmless chemical.

 

Sawflies have their own fan club.  Most species are picky eaters with specific plants they use.  They get the "saw" from the female's ovipositor used to insert eggs into the plant tissue.  There is a lot of variation in the organ and how deeply they plant the eggs.  The Bug Lady describes how they use their little saw and create their waxy disguise.

"Females saw into the mid-rib of leaflets and deposit 20 to 30 eggs, one at a time, which eventually causes the leaflet to droop or fold and the midrib to turn pale; and while small larvae chew random holes in leaves, larger ones may finish them off entirely, leaving bits of the larger veins behind.

 

Unadorned larvae hatch in about a week and commence producing waxy, white fronds to adorn themselves. Each molt leaves the feathery skin behind, and the larva must cloak itself anew. Finished growing, they drop to the soil. The pre-pupal larva forms a cocoon in which it overwinters in a state of suspended animation (aestivation), pupating in spring. The cycle is completed when adults emerge in early summer."

The next time you see white bird dropping on a leaf, look a little closer.