New Mexico Scarab?

[bethanyfarah]

This little lovely was found in a pitfall trap at the Jornada Experimental Range near Las Cruces, New Mexico, USA. I'm pretty sure this is a male of some kind because of the shape of the head. The grid he's resting on is a 1cm×1cm grid on the bottom of a petri dish, so he's about .5cm long. imgur.com/gallery/5mDL4Da

[Adam Cotton]

Wow, that is very interesting. I agree, it looks like a male to me too; unfortunately I know very little about beetles, but it does look like a member of family Scarabeidae. I suspect that bandrow may be able to help identify it, but it's a pity there are no dorsal photos.

Adam.

[bandrow]

Greetings,

Your beetle is Euoniticellus intermedius (Reiche) - a species intentionally introduced into the U.S. from Africa around 40 years or so ago. It can be fairly common in some areas of Texas and Arizona. And you're correct - it is a male.

One suggestion - when taking images, try to get at least one direct dorsal shot as well as the lateral and ventral. This guy was IDable based on your images, but often a dorsal view is critical for an ID.

Cheers!
Bandrow

[Adam Cotton]

Nov 20, 2020 7:35:04 GMT -8 bandrow said:

Your beetle is Euoniticellus intermedius (Reiche) - a species intentionally introduced into the U.S. from Africa around 40 years or so ago. It can be fairly common in some areas of Texas and Arizona. And you're correct - it is a male.

I am curious to know why it was intentionally introduced. Was it to control an invasive plant?

Adam.

[bandrow]

Hi Adam,

There have been several species of Scarabaeinae introduced intentionally to purportedly "assist" the native fauna of dung beetles in processing dung faster in pasture and ranch settings. Cycling the dung into the soil helps minimize "burn" of grasses from dung pats sitting on it and helps return nutrients to the soil. These introduced species evolved on the plains of Africa with massive numbers of large herbivores, so are pretty efficient at processing dung. Our native species did not evolve in an environment populated by millions of cattle, as so much of our rangeland is now, so are more restricted in their 'dung of choice'. 

There is some indication that the exotics have put pressure on native species, outcompeting them, but I'd have to check the literature for specific examples...

Cheers!
Bandrow

[Adam Cotton]

Thank you for the interesting explanation. I didn't realise that this is a dung beetle, it looks more like a tiny version of Oryctes, hence my question about invasive plant control.

Adam.

[bethanyfarah]

Bandrow,

Thank you so much for the id! The fact that they were introduced from Africa helps explain why I was struggling to find it. The Jornada is also a long term research cattle range, so I can't say I'm surprised that they took a page out of the Aussie's book and introduced dung beetles to help control the waste. I wonder how the non-natives alter nutrient cycling in our delicate desert grasslands?

Thanks for the advice about the photos! I'm still a little new to entomology and can use all the advice I can get (though having dorsal photos does seem a little obvious now that you mention it lol)

Bethany

[bandrow]

Hi Bethany,

Glad to help! The first time I collected Euoniticellus myself, in Texas, I was stumped too. The other really common exotic is Digitonthophagus gazella - I think it now occurs all the way across the southern U.S., and can be abundant.

I've always found it intriguing to wonder what kind of dung beetle fauna was associated with the American bison before man nearly wiped them out. I've heard anecdotally that there was a now-extinct Phanaeus species associated with them, but I can't find any evidence in the literature of that. Probably a "grassland" legend, or some scarab worker's fantasy!

I guess the question as to how they alter the nutrient cycling in delicate grasslands is complicated by cattle being introduced into those areas in the first place. Many of the scarabs one finds in cattle dung are introduced species, or species in the genus Phanaeus and Canthon. I'm guessing that these two genera may have evolved with bison and shifted to cattle over time. But I have found both of these genera in big numbers in areas with few or no cattle, so they must utilize other dung sources as well. So, in grasslands with no cattle, I'm not sure what species composition could be expected.

Are you running pitfalls as part of an organized study, or for your personal interests? What taxa are you specifically trapping for?

Cheers!
Bandrow

[bethanyfarah]

Bandrow,

I was a temporary field technician for the National Ecological Observation Network (NEON) for two years. We use pitfall traps to collect carabid beetles, but we sort out and save all the other arthropod bycatch. The bycatch is stored at a respiratory at Arizona State University and the samples and data are all available for anyone to use for research. www.neonscience.org/samples Beetle sorting was my favorite protocol ever because I got to spend 40hrs a week looking at all the weird inverts in our trap samples. (Have you ever seen a solgifuge under the microscope? It's like a cute fuzzy nightmare)

But look what I found in my personal collection! Another Euoniticellus intermedius? imgur.com/gallery/agfKvZb I found this guy in my in-laws' pool in Tucson earlier this year. It could be a female or a minor male? It's hard to say without popping it under the microscope (also sorry about the terrible lighting)

I've never really thought much about what kinds of dung beetles went extinct with the reduction of bison herds. A Phaeneus would be wonderful, but I doubt we'll have proof of its existence anytime soon.

Cattle greatly damage arid grasslands, but I always thought it was about erosion and not nutrient cycling? Hmmm... I know if it wasn't for the damage cattle does we woulnt even have these long term research stations; Santa Rita Experimental Range and the Jornada Range were both founded to address the issue of desertification of arid grasslands due to the introduction of cattle. In the Southwest I know deer and antelope live on the grasslands when there are no cattle, and in the recent fossil record we had some really big mammals that lived in the area, so maybe we have some generalist species that were able the switch to drier deer dung until we brought cattle to the area?

Here is another photo of some of the species I found in a catch cup that had been partially filled in with a cow pie. You can see we have a variety of species, but I wonder how many are native. imgur.com/gallery/nNCauWJ

[bandrow]

Hi Bethanyfarah,

Small world!! I work at the Carnegie Museum in Pittsburgh and our recently retired Collection Manager, Bob Davidson, has been the carabid identifier for the eastern domains for NEON for a number of years now. A good friend, Kip Will, has been handling the western domains.

Your specimen of Euonitocellus looks like a female to me. In your images of the other scarabs, it appears as if there are 3, if not 4, species of Canthon. The smallest ones could be Onthophagus sp., but I can't quite make them out. There is also an Omorgus in the image - a typical knobby specimen of Trogidae. All of the species in the image are natives.

I run dung pitfalls often and I'm always amazed by both the diversity in species and the numbers of individuals in the right habitats. Dung beetles are one of the cooler taxa and fun to collect, once you make peace with your olfactory senses...

Cheers!
Bandrow