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longhorn - Crossidius discoideus

longhorn - Crossidius discoideus
Peyton, El Paso County, Colorado, USA
August 18, 2007
Size: 15 mm
Is this a Milkweed Longhorn?

Images of this individual: tag all
longhorn - Crossidius discoideus longhorn - Crossidius discoideus


Crossidius discoideus sayi Casey 1912

Moved from Crossidius.

On milkweed?
I am curious, did you find it on a milkweed plant?
I lightened the image a little so the details can be seen better.

Found it on...
Composita. Along with many other beetles.

The species...
...feeds on Gutierrezia and Haplopappus (Asteraceae) - larvae bore in the root crown while adults are found on the flowers and foliage.

Longhorn , yes
Not a milkweed species tho, my guess is this is something in the genus Crossidius

Thanks Guy,
In fact it may be Crossidius pulchellus.

Harvard image reference here. I noticed that the pronotum coloration is different though.

not pulchellus
Its definitely not pulchellus. My initial thought was possibly some subspecies of C. coralinus. This species is quite polymorphic (occurs in many different patterns) depending on the population location.

I agree
Tom Murray has one on his site that is similar.

I believe this is...
Crossidius discoideus. Populations in east-central Colorado would be assignable to subspecies sayi, which occurs from western Kansas through the southern Rocky Mountain region.

Another voice for subspecies sayi
Beyond locality here, the black maculation on the pronotum is also consistent with subspecies sayi, and inconsistent with the other two subspecies.

That's according to the literature...from 100+ years ago. I was studying this today, and edited the C. discoideus info page to reflect what I learned. But it would be nice to to have my interpretation of the literature checked by someone who's familiar with possible developments in the taxonomy of the group in the last century, and who could correct or confirm my edits to the info page earlier today!

I guess I stepped in it there, now that I have my keys in front of me that makes more sense with the pronotal maculations, My specimen of discoideus I have in my collection does not show that much marking.

I appreciate...
All the fine work you guys (no pun intended) have done.

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