Robin’s carpenterworm

(Prionoxystus robiniae)

Robin's carpenterworm
Photo by Bill Reynolds
  Hodges #


Conservation Status
  IUCN Red List

not listed


NNR - Unranked


not listed


Robin’s carpenterworm is a medium-sized moth but a very large micromoth. It is similar in size and appearance to a sphinx moth and is often misidentified as one. Adults are 11 16 to 1¾ long with a wingspan of 17 16 to 3. The female is much larger than the male.

The body is heavy. The abdomen extends well beyond the hindwings.

The forewings on the female are more or less triangular and rounded at the tip. They are pale gray and semi-translucent with a dense, net-like overlay of thin, dark lines and, in the basal and median areas, wider lines that fill in the blank areas creating dark blotches. They have an accessory cell and 2 anal veins that are complete, extending from the base to the margin. Some of the veins branching off of the “R” vein are stalked. The forewings of the male are similar but narrower and more pointed at the tip. The hindwings of the female are as wide as the forewings but much shorter. They are similar in color to the forewings but with a less distinct overlay of thin lines and no wider lines. They have 3 anal veins. The hindwings of the male are similar in shape, black from the base to the median area, bright yellowish-orange from the median area to the submarginal area, and bordered with a thin black marginal line. The hindwings and forewings are held in contact by bristles (a frenulum) and scales (a retinaculum).

The head is gray. There are no mouth parts and no hearing organs. The antennae on the male are feathery, with extensions along both sides of the central axis (bipectinate). On the female the antennae are thread-like.

The legs are black with white bands. There is a large spine (spur) at the tip of the fourth leg segment (tibia).

The caterpillar is 2 to 2¾ long. It may be greenish-white with a dark brown head and thoracic shield, or pinkish with scattered dark spots and a reddish-brown head and thoracic shield.




Wingspan: 17 16 to 3

Total Length: 11 16 to 1¾


Similar Species


Deciduous and mixed forests, hardwood shelterbelts.




May through July




Adults are attracted to light.


Life Cycle


The female lays eggs singly or in groups in the crevices of the bark of a host tree. After hatching, the caterpillars feed by boring into the cambium layer of the tree. This creates galleries and tunnels under the outer bark that decrease the value of the wood and can sometimes kill the tree. Wood has little nutritional value. As a result, the caterpillar takes 3 or 4 years to complete its life cycle. It pupates in the spring of its final year and emerges as an adult between May and July.


Larva Hosts


Ash, black locust, oak, poplar, and willow


Adult Food


Adults do not feed


Distribution Map



21, 24, 29, 75.




Widespread but uncommon



Lepidoptera (butterflies and moths)  




  Parvorder Heteroneura  
  No Rank Ditrysia  
  No Rank Apoditrysia  













Common Names



carpenterworm moth

locust borer

Robin’s carpenterworm











A spine (male) or multiple spines (female) at the base of the costal edge of the hindwing of many moths that couples with the retinaculum on the forewing to keep the wings in contact which each other.



The fourth segment of an insect leg, after the femur and before the tarsus (foot).






Visitor Photos

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Bill Reynolds
  Robin’s carpenterworm   Robin’s carpenterworm Photos



  Prionoxystus robiniae (Robin's Carpenterworm)
Allen Chartier
  Prionoxystus robiniae (Robin's Carpenterworm)  



Visitor Videos

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Bill Reynolds
  Robin's carpenterworm (Prionoxystus robiniae)
Published on Dec 18, 2015

The first two images, if you notice, the wings are blurred and the back end. It is vibrating it's muscle and getting ready for take off. The video is the … moth revving up.

Location: Pennington Co., MN

Video by Bill Reynolds

Other Videos
  Carpenterworm Moth (Cossidae: Prionoxystus robiniae) on Wall
Carl Barrentine

Uploaded on Jun 21, 2011

Photographed at Fisher, Minnesota (21 June 2011). Thank you to Maury Heiman ( for confirming the identity of this specimen!

  You're Just Too Good To Be True...Can't Take My Eyes Off You...
Carl Barrentine

Uploaded on Jun 24, 2011

A Crab Spider (Xysticus) sizes up a Carpenterworm Moth (Prionoxystus). ;-) Photographed at Grand Forks, North Dakota (24 June 2011).

  Robin's Carpenterworm Moth (Cossidae: Perionoxystus robiniae) Lateral View
Carl Barrentine

Published on Jun 2, 2012

Photographed at Grand Forks, North Dakota (02 June 2012).

  Carpenter Moth (Cossidae: Prionoxstus)
Carl Barrentine

Uploaded on Jun 7, 2010

Photographed at Grand Forks, North Dakota (06 June 2010).




Visitor Sightings

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Bill Reynolds

Location: Pennington Co

… the wings are blurred [on] the back end. It is vibrating it's muscle and getting ready for take off.

Robin’s carpenterworm






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