Japanese burrowing crickets have arrived in Colorado (& other musings)
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Ted Floyd
Oct 3, 2025, 2:26:38 PM (7 days ago) Oct 3
to Colorado Birds
Hey, all.
By the way, you can hear the reverb (and see it in the spectrogram) of the tree cricket. 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:
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. 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, 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:
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:
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:
That's Megatibicen dealbatus, the plains harvestfly, and I recorded it yesterday whilst photo'g the hummer. 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.
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:
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:
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, 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, too. And I went back out last night, Thurs., Oct. 2, with better recording gear, and I got a cleaner recording 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:
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:
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, 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, too. And I went back out last night, Thurs., Oct. 2, with better recording gear, and I got a cleaner recording 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:
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:
By the way, you can hear the reverb (and see it in the spectrogram) of the tree cricket. 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:
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. 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, 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:
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:
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:
That's Megatibicen dealbatus, the plains harvestfly, and I recorded it yesterday whilst photo'g the hummer. 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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