On the trail of Pero morrisonaria (H. Edwards 1881)

Pero morrisonaria (Hy. Edwards, 1881)

I was going through my images from 2015, looking to dispose of as much excess as possible in order to make space on my hard drive when I came across a few moth images that I had forgotten about. This is probably my favorite so far — Pero morrisonaria (H. Edwards, 1881) from the family Geometridae, which was caught at a light in our Edmonton garden May 30 last year. (Thanks to Gary Anweiler for the ID) On a white background, the pattern is very distinct, yet on bark we can see how useful this mottled earth-tone pattern is.

Pero morrisonaria (Hy. Edwards, 1881)

Pero morrisonaria (Hy. Edwards, 1881)

Morrison’s Pero is considered common and is found across the US and Canada. The caterpillars are twig mimics and feed mostly on fir and spruce, but have also been found on a variety of broadleaf plants such as alder and willow.

An interesting feature on this moth is the partly ‘rolled’ leading edge of the forewing, and I wonder if this has the effect of strengthening its cryptic appearance or aerodynamics or if it serves another function.

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N.B. For what is to follow, I advise caution: I am not an entomologist or a taxonomist, or a lepidopterist for that matter. Some may find this simplified trail of taxonomy (classification and nomenclature) interesting, others may find it ridiculous. I pursued it out of idle curiosity, because I appreciate history and the work of taxonomists, and because sometimes I’m a buffoon for science.

I have a vague memory of certain conventions of nomenclature, so when I saw the name “Pero morrisonaria (Hy. Edwards, 1881)“, I knew that “Hy. Edwards” indicated that he was the first to name this moth,  that the first record that he did so was published in the year 1881. and that he had used certain morphological (i.e. the form and structure) characteristics to distinguish it from other similar moths. Also, because the name “Hy. Edwards”  was placed in brackets, it indicated that the moth’s name had been changed in some way since then. I also knew that there were perhaps other taxonomists named “Edwards” whose first name began with “H”, and that “Hy” was used to distinguish him from the other Edwards’s. I decided to see if I could find out why the name had changed, and for that I began at that amazing resource, The Biodoverity Heritage Library.

I found the original description by Henry Edwards, in Descriptions of some new species of Heterocera, Family Geometridae, published in the journal Papilio, (1881, Vol 1, pg 121), where he placed it in genus Azelina, with the species name “Morrisonaria” after H.K. Morrison who collected the specimen in the Washington “territory” (which in 1883 became the State of Washington).

Henry Edwards-001

Click to enlarge.

The genus Azelina was first created by Guenée in 1857, however, the entomologist Herrich-Schäffer, had already assigned similar moths to the genus Pero earlier in 1855, The difference between these sister taxa (and others) was based mostly the antenna, wing shape and wing venation, although in other regards they looked similar.

At this point it is good to keep in mind that The International Commission on Zoological Nomenclature (ICZN) was founded in 1895, although talk of an international code for nomenclature began in 1842. One of the goals of the code is to maintain–as much as possible–stability in names. In the 4th edition of the code (1 January, 2000) it is recommended that in most cases Latinization not be corrected, including, “…names based on personal names with incorrectly Latinized endings,… as this would cause instability”. (See the exceptions at: What is the correct original spelling?)

Noting how “perplexing” the genus Pero/Azelina had become, John A. Grossbeck of the Experimental Station of New Brunswick, New Jersey set out to refine genus Pero as it was represented north of Mexico. He used specimens from his own collection as well as those he obtained from other lepidopterists, including  about 300 specimens from Dr. William Barnes, a famed collector of the period. For his paper, Studies on the North American geometrid moths of the genus Pero (1911), Grossbeck examined about 800 specimens from which he identified 9 different species, 4 of which were new.

Plates from North American Geometrid Moths--Grossbeck

Plates from North American Geometrid Moths–Grossbeck

Grossbeck used male genitalia (above right, click to enlarge) as the primary way to distinguish the species, and on that basis Azelina was pulled into Pero. Henry Edwards’ Azelina morrisonaria become Pero morrisonatus–and that’s why ‘H. Edwards’ is now shown in brackets. But why the change from “morrisonaria” to “morrisonatus”?

Studies on the North American geometrid moths of the genus Pero by Grossbeck

Click to enlarge

We can see that (detail, above left) Grossbeck introduces his description by listing Edwards’ paper, as well as that of G.D. Hulst, who in 1886 saw fit to make A. morrisonaria a synonym of Azelina hubnerata in his paper, Notes on the various species of the Ennominae (below).


Also noted in Grossbeck’s  introduction  was that in 1902, H.G. Dyar’s paper, A list of North American Lepidoptera and key to the literature of this order of insects (below) listed Azelinamorrisonata” as a synonym of A.ancetaria, which is a different spelling from Edwards’ original species name  A. morrisonaria.  Did Dyar make the first mistake?

List of North Americas Lepidoptera by Dyar

Click to enlarge.

Did Grossbeck carry forward Dyar’s change when preparing his 1911 paper? It does appear that way, because he lists Henry Edwards 1881 species name incorrectly as Azelina morrisonata. Below is the trail: (Click first photo for slide show)

The specific epithet has changed from morrisonaria to morrisonata then to morrisonatus. Were these mistakes, or did the authors feel they were correcting a Latin error? I don’t know. Let’s look at two examples of what happened to Morrison’s Pero after 1911. Take a look below at Canadian, J. H. McDunnough’s Critical notes on certain Pero species (Lepidoptera, Geometridae) (1949), where this happens:

Critical Notes on certain Pero species by McDunnagh 1949

Click to enlarge

We now have a fourth name for our common moth, Pero morrisonarius! Another mistake or a reasoned correction? I still don’t know.

I’ll close with a more recent paper, A Taxonomic Revision of the New World Moth Genus Pero (Lepidoptera: Geometridae) by Robert W. Poole.(1987). We are now under the reign of the 4th edition of ICZN, and 106 years after Henry Edwards’ original description:

Critical notes on certain Pero species by J.H. McDunnough

Click to enlarge

Well, there it is! “Misspelling”. We have arrived at Pero morrisonaria (H. Edwards 1881) — and that was the point, wasn’t it?

But wait–what happened to “Hy. Edwards”?



(Most  of the information for this post can be found in the inline links.)

BugGuide (Today, according to BugGuide, Pero contains 18 species in North America)

E.H. Strickland Entomological Museum— Entomology Collection

ITIS Report





This entry was posted in Alberta, Bugs, Canada, Education, Geometridae, History, Insect, Lepidoptera, photography, Season, Winter and tagged , , , , , , , .


  1. Gary Anweiler 29 January, 2016 at 2:26 PM #

    Wow….well done! You even have my head spinning… and I read this stuff all the time! It IS obvious that you are suffering from a lack of live bugs to shoot out in the wilds.

    One more bit of info. I believe the wrinkles in the forewing is a mimicking of the way dead dry leaves twist and curl… and along with the erratic forewing margin and wavy forewing pattern it makes for excellent mimicry!

    • Adrian 1 February, 2016 at 3:51 PM #

      I confess to kind of enjoying the process, I just wish it had an outcome that was actually useful!

  2. Charles Bird 29 January, 2016 at 5:29 PM #

    Well done Adrian. Most of us just accept the spelling and authorship in the latest checklist. You have clearly shown that there is often much more to it than that.

    • Adrian 1 February, 2016 at 4:09 PM #

      Thanks Charlie. I was surprised myself how often mistakes were passed along.

  3. Annie Pang 30 January, 2016 at 2:20 AM #

    Wow! My head is spinning. What an amazing moth. I think Gary is right about the rolled up edges of the forewings. Very thoroughly researched, Adrian!

    • Adrian 1 February, 2016 at 4:11 PM #

      Thanks, Annie! I have to challenge the brain-cells on occasion!

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