Date: 10/3/25 11:26 am From: Ted Floyd <tedfloyd73...> Subject: [cobirds] Japanese burrowing crickets have arrived in Colorado (& other musings)
Hey, all.
I was out and about in Lafayette, Boulder Co., yesterday evening, Thurs.,
Oct. 2., and I cellphone-photo'd this *great horned owl,* bathed in the
halo of the waxing gibbous moon, along the path:
[image: Great Horned Owl.png]
There was a Riley's tree cricket, *Oecanthus rileyi*, singing from a little
Russian olive, *Elaeagnus angustifolia*, directly ahead, which reminded me
of something Nathaniel Hawthorn once wrote:
"If moonlight could be heard, it would sound just like that.”
Hawthorn seems to have had in mind the snowy tree cricket, *O. fultoni*,
common in New England and elsewhere, in his paean to cricketsong. I'll have
more in a bit about *Oecanthus* tree crickets, but for now, let's talk
about the Japanese burrowing cricket, *Velarifictorus* *micado*. Back on
Thurs. evening, Sept. 25, 2025, I audio-recorded what appears to be
Colorado's first <https://www.inaturalist.org/observations/318228905>, on
the University of Denver campus, Denver Co. And it wasn't alone; others
were going off in the immediate vicinity. Then, back on this past Wed.
evening, Oct. 1, I heard several in Lafayette, and I audio-recorded one of
those <https://www.inaturalist.org/observations/318222486>, too. And I went
back out last night, Thurs., Oct. 2, with better recording gear, and I got
a cleaner recording <https://www.inaturalist.org/observations/318407805> of
one singing in Lafayette.
The Japanese burrowing crickets have arrived! Yay! Yay? Well, they're
invasive and nonindigenous, so perhaps not. They're the gryllid counterpart
of the Eurasian collared-dove. Can I get a woohoo! Again: Perhaps not. In
any event, I wonder whether these burrowing crickets might soon be one of
the dominant night sounds in the Denver metro region. How soon? How about
within a year or so? I'm reminded of how, several years back, Andrew Floyd
and I found one (*n*=1) ebony jewelwing, *Calopteryx maculata*, in the Coal
Creek drainage, Boulder Co.; the next summer, Mikaela Caldera documented
almost 100 along the creek; and the summer following that, there were
thousands up and down the length of the creek. Will the burrowing crickets
do likewise? You heard it here first...
And how, pray tell, do you distinguish the chirping of the Japanese
burrowing cricket from that of the Riley's tree cricket—or any other
cricket for that matter? Well, that's where the fun begins. In a nutshell,
you can do it with your phone. Now there's not a Merlin-like app for
cricketsong (not yet anyhow), so you have to do a wee bit of analysis on
your own. But I, personally, have found doing so to be a wonderful learning
experience. Each cricket has a chirp rate and a so-called "carrier
frequency" (older term, and not a good one; the cricket people are going
over to "dominant frequency," and I think that's good); combine those two
parameters with the ambient temperature (very important), and, in most
instances, you've got it down to just a handful of species already.
Resolving species-level differences sometimes requires taking a look at
something called the pulse pattern.
Case in point: last night's burrowing cricket. Chirp rate, 220 min.⁻¹;
carrier (dominant) frequency, 2.9 kHz; temperature, 18 °C. And last night's
tree cricket: chirp rate, 84 min.⁻¹; carrier (dominant) frequency, 2.2 kHz;
temperature, 17 °C. And the unique pulse patterns seal the deal: 1-5 for
the burrowing cricket, and a highly distinctive alternation between 2-3-3-3
and 2-3-3-3-3 for the tree cricket.
Here's a spectrographic snippet from last night's burrowing cricket,
indicating the fairly straightforward 1-5 pulse pattern:
[image: Velarifictorus micado.png]
And here's a spectrographic snippet from last night's tree
cricket, indicating the alternation between the 2-3-3-3 and 2-3-3-3-3 pulse
patterns:
[image: Oecanthus rileyi.png]
By the way, you can hear the reverb (and see it in the spectrogram) of the
tree cricket <https://www.inaturalist.org/observations/318407817>. How cool
is that! Anyhow, the spectrograms of the tree cricket and burrowing cricket
are totally different, but a few of us (Scott Severs, you out there?) might
be wondering about something: What about the snowy tree cricket, the one
Hawthorne wrote about? The situation is complex; it's "breaking news," you
might say. Apparently, the snowy tree cricket was rather common in the
Front Range metro region until quite recently. But Riley's tree crickets
have recently invaded from points west and south, and they are perhaps
displacing our snowy tree crickets. Here's a recent range map from the
brilliant Singing Insects of North America (SINA) website
<https://orthsoc.org/sina/>:
[image: rileyi range map.png]
But they're here now, distinguished by their unique pulse pattern, as well
as carrier (dominant) frequencies and chirp rates that differ from those of
the snowy tree cricket. And the thing with the chirp rate is especially
curious. The snowy tree cricket is the fabled "thermometer cricket," whose
chirp rate exhibits near-perfect linear dependence (< ±1 °F) on ambient
temperature. There's even a scientific "law" that governs this. It's called
Dolbear's Law.
Well, it all works great in New England, where Amos Emerson Dolbear and,
for that matter, Nathaniel Hawthorne delighted in the songs of snowy tree
crickets. But it gets messy where snowy and Riley's tree crickets come into
contact. Intriguingly, the Riley's tree crickets in the Front Range metro
region seem to sing at a rate intermediate between the "official" chirp
rates for the two species. We're working on it... If you want to dive deep
into the weeds on this one, check out the Thermometer Crickets Page at SINA
<https://orthsoc.org/sina/588thermometer.htm>. I couldn't make this stuff
up.
By the way, the most famous nighttime chirper of all has to be *Gryllus
pennsylvanicus*, the fall field cricket. I recorded one last night in
Lafayette <https://www.inaturalist.org/observations/318407806>, with these
specs: chirp rate, 88 min.⁻¹; carrier (dominant) frequency, 4.6 kHz;
temperature, 17 °C. This species has a characteristic 1-3 pulse pattern, as
indicated by this spectrographic snippet from last night's audio:
[image: Gryllus pennsylvanicus.png]
I suppose I ought to say a bit more about birding, eh? Well, the
hummingbirds are still putting on a good show at Greenlee Wildlife Preserve
in Lafayette. It seems that most of the hummers still hanging on are
hatch-year males, and what's cool about hatch-year males at this time of
year is that they're beginning to acquire adult plumage. Like this
male *black-chinned
hummingbird* in fading light yesterday afternoon, Thurs., Oct. 2, at the
preserve:
[image: BCHu 01.jpg]
Although this little fella is perched at a feeder, he was spending much of
his time catching flying insects. Quick! To the phones! Where's Leatherman
when ya need 'im? Not sure what insects the hummer was murdering, but it
definitely wasn't this one:
[image: Megatibicen dealbatus.png]
That's *Megatibicen dealbatus*, the plains harvestfly, and I recorded it
yesterday whilst photo'g the hummer
<https://www.inaturalist.org/observations/318407804>. Can you say
multi-tasking or what. Anyhow, *M. dealbatus* is not a cricket, but,
rather, a cicada. Oh, and before we proceed, the specs: chirp rate, 168
min.⁻¹; carrier (dominant) frequency, 5.0 kHz; temperature, 27 °C. (Pulse
pattern, as *per* crickets, does not apply in the case of cicadas.) Anyhow,
like seemingly every other species of organism in the Front Range metro
region, the plains harvestfly is in the process of a range shift. We Floyds
heard these rarely at best when we moved to Lafayette a bit under 20 years
ago, but now they are common on warm afternoons in late summer and early
autumn. They're far too big for hummingbirds (duh), but they're not too big
for Mississippi kites. Which point I raise in connection with the striking
correlation between the northward expansion of that marvelous raptor and
that of the deafeningly loud harvestfly. Yes, the kites eat the
harvestflies, and it is remarkable to watch them hovering, like humongous
hummingbirds, in front of big shade trees in Lamar or even Denver where
they glean harvestflies from the foliage.
Okay, I imagine Suddjian's getting impatient with me by now, so I'm audi.
Catcha next time. Peace, —Floyd out
Ted Floyd
Lafayette, Boulder Co.
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