butternut woollyworm

(Eriocampa juglandis)

Conservation Status
butternut woollyworm
Photo by Luciearl
  IUCN Red List

not listed


not listed


not listed


Butternut woollyworm is a common sawfly. It occurs in the United States east of the Great Plains and in southern Ontario and Quebec. It is most common in the northeast, rare in Minnesota. The larva is host-specific, feeding almost exclusively on the leaves of butternut and black walnut, though it has been collected on hickory in the northeast. Adults feed on pollen, nectar, honeydew, sap, and other insects.

Females are 5 16 (7.7 to 8.4 mm) long. Males are smaller, ¼ (6.3 to 6.8 mm) long.

The head is mostly black. The sensory organs on the upper jaw (labial palpi) and lower jaw (maxillary palpi) are brownish. The antennae are thread-like, stout, and mostly black. They have 9 segments. Segment 2 is longer than wide. Segment 3 is longer than segment 2. Segments 5 through 9 are reduced in size and are brownish on the underside. Segments 7 and 8 are not broadened at the tip.

The body is robust and entirely black. The thorax and abdomen are broadly connected. The middle thoracic exoskeletal plate (mesoscutellum) is covered with deep, closely spaced punctures. The female has a saw-like ovipositor at the tip of the abdomen.

The wings are mostly clear and evenly tinged brown. On the forewing, the anal crossvein is oblique. On the hindwing both the radial sector (Rs) cell and the media (M) cell are present. On the male the hindwing does not have a peripheral vein.

The legs are long and slender and mostly white. The basal half of the first segment (coxa) of each leg is black. The second segment (trochanter) has two segments. On the hind leg the end third of the third segment (femur), the end third of the fourth segment (tibia), and the tip of the last section (tarsus), are black. On the front leg the tibia has two spurs at the tip.

Late stage larvae are to 1316 (15 to 21 mm) long. The head capsule is white with two black eye spots. The body is densely covered with white, cottony or woolly, hair-like processes (flocculence). This feature gives the species its common name. The flocculence is shed with each molt. Late stage bare larvae are pale green.




Male: ¼ (6.3 to 6.8 mm)

Female: 516 (7.7 to 8.4 mm)


Similar Species






One generation per year in Minnesota: July and August






Life Cycle




Larva Food


Leaves of mostly black walnut and butternut, but it has also been reported on hickory.


Adult Food


Pollen, nectar, honeydew, sap, and other insects.


Distribution Map



24, 29, 30, 82.




Uncommon throughout its range, rare in Minnesota



Hymenoptera (ants, bees, wasps, and sawflies)  


Symphyta (sawflies, horntails, and wood wasps)  


Tenthredinoidea (typical sawflies)



Tenthredinidae (common sawflies)




  Tribe Eriocampini  





Selandria caryae


Common Names


butternut woollyworm (larva)

butternut woollyworm sawfly (adult)










On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.



Short for pedipalp. A segmented, finger-like process of an arthropod; one is attached to each maxilla and two are attached to the labium. They function as sense organs in spiders and insects, and as weapons in scorpions. Plural: palpi or palps.



On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.



The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.






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Other Videos
  Butternut Wooly Worm - The Cutest Larva? Nature Now!
Nature Now! - Chris Egnoto

Jul 8, 2017

Well what have we here? We have ourselves some Butternut Wooly Worms! (Eriocampa juglandis) These neat little things look like something you catch with a Pokeball...at least they do to me. Wooly Worms are the larval form of a type of sawfly. Sawflies get their name from a saw like aperatus used for depositing eggs and they are related to bees and wasps. These wooly worms have a waxy secretion on their backs that looks something like fluffy ribbons. I really hope you get as much fun looking at these guys as I did!!

  The bizarre Butternut Wooly Caterpillar astonishes onlookers!

Sep 8, 2016

Nature never ceases to amaze and bewilder me. As a professional Naturalist, I am surrounded by the natural world year-round and I continually encounter creatures I have never seen, nor heard about - or saw in photographs in my lifetime. It stands to reason, since there are countless varieties of animals and insects in my state alone. This time, encountering these wispy, spooky, "cotton-like" critters on a shrub beside me during a morning walk, they didn't seem alive. They seemed like some sort of frayed fabric caught among the leaves as strange, fluffy white strands swayed in the breeze. But they certainly *were* alive! They began to crawl across the leaves, appearing much like a caterpillar variety. But why the fluffy exterior? What purpose did it serve? I was compelled to capture HD video of these alien creatures with a macro lens. After much searching and consulting, I found out they were the elusive "Butternut Woolly Sawfly Caterpillars" - Eriocampa juglandis. They wouldn't become a butterfly or a moth as I had assumed. Instead, they would become a bizarre wasp variety called a "Sawfly". Their spooky appearance leaves me wondering how many times I will encounter creatures unknown in my future.




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Location: Cass County

butternut woollyworm  
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Created: 10/1/2020

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