Unidentified beetle
Location: West-central New Mexico, 7100’ elevation, pinyon/juniper forest
July 8, 2011 11:03 am
My husband says it’s a cockroach, I say, no. What say you?
Signature: Mary

Root Borer

Hi Mary,
We hope he is taking you for a nice romantic dinner for winning the bet.  This is NOT a cockroach.  This is a Root Borer in the genus
Prionus, and a very likely candidate is Prionus heroicus. It looks like this picture on BuGGuide and though BugGuide has no reports from New Mexico (we would urge you to submit yours) it is found in neighboring Arizona and Utah.  Your elevation might be a key factor in identifying the species.  We like this comment:  “Male individuals of Prionus (Homaesthesis) rarely get this large – the subgenus is distinguished from Prionus (s. str.) by the opaque, non-striolate poriferous areas on the antennae, smaller size (usually less than 30 mm), and less strongly expanded pronotal margins.  Prionus californicus is typically more reddish – the darker coloration of this specimens makes me think it might be Prionus heroicus.  There is no such name as Prionus derobrachus. Derobrachus hovorei is the new name for the species formerly known as Derobrachus geminatus. The species formerly called Derobrachus forreri is the true Derobrachus geminatus.
… Ted C. MacRae, 29 August, 2007 – 11:50am” from BugGuide.  We wondered if this might be P. californicus, but the part of the dark coloration distinguishing the BugGuide photo seems to apply to your specimen, also a male.  An eastern relative, the Broad Necked Root Borer, is our featured Bug of the Month and beetles in this subfamily, Prioninae, have been most plentiful this year.  We would not like to aggravate a male Prionid as they have strong jaws and we suspect some species may be able to draw blood in a human.
P.S.  It looks smashed, so we are tagging this Unnecessary Carnage.

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Location: New Mexico

6 Responses to Root Borer

  1. Kelly Boone says:

    I found three of these things in ONE hole in a Pecan Tree in Texas, about an hour east of San Antonio, in Seguin. They match all of the photos I seen on the net. It says the larva feeds on the roots but the hole was at least 7 feet off the ground.

    • bugman says:

      We believe they will also bore in the trunks of trees, and seven feet from the ground is not very high for a large nut tree.

  2. Steve Marcus says:

    Found a RB Beetle in my garage munching on (or trying to eat) the carpet which lines my cat’s “kitty condo”. Got some nice pics if you want.
    Steve in Prescott Valley, Arizona

  3. Rebecca Torres says:

    I found one of these today on my front porch. I live 10 mins north of Albuquerque. I have lived in this area my whole life and have never seen one of these.

  4. Ruth Metzger says:

    I found a beetle on my patio that looks like the picture in bugguide and it indicates that it is a Prionus heroicus long horned beetle in the family Cerambycidac. How do I determine if there are more in my area and what do I do to get rid of them.

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