Weevil camouflaged as bird dropping

2011 August 27

It squeaks!

Here’s a beetle Sam found on the side of the house on June 27, 2011. She thought it was a bird dropping at first until it moved, and now she calls it a “Poo beetle”.

From the elongated snout, it is clearly one of the snout beetles in the family Curculionidae, and I think it is a “Poplar and Willow Borer”, Cryptorhynchus lapathi.

It’s another European invasive species. It chews holes in the bark of willow and several species of poplars, and lays its eggs in the holes, where the larvae spend a year or two burrowing under the bark and through the wood, pushing out little piles of sawdust. They weaken the stems of the trees they infest, and young trees in particular become likely to snap off in the wind.

In addition to looking, at first glance, like a bird dropping, it has another amusing feature. When it is picked up, it stridulates by rubbing its body segments together. This makes it vibrate, and if you hold it up to your ear, you can hear it making a faint “vip, vip, vip” sound. Here’s a recording:


Since the beetle was so quiet, I had to goad it into squeaking while it was pretty much standing directly on the microphone of the recorder I was using[1]. I also had to chase the kids outside and barricade myself in the bathroom to get a low enough level of background noise that the beetle squeaks would be the loudest thing in the recording.

There are a bunch of different beetles that make this sort of noise, mostly various kinds of longhorn beetles. In particular, the Red Milkweed Beetle does this, I used to play with them as a kid and hold them up to my ear to hear the sound. Oddly, this stridulation doesn’t seem to get mentioned very often when people describe beetles that do it. Maybe because the sound is faint, and most people don’t hold beetles up to their ears.

[1] I recorded this with a little RCA VR5320R Digital Voice Recorder. This is a basic cheap recorder [2] that stores sound directly as .wav files, rather than having to extract a sound file from a video recording (which is what I had previously done, using the microphone on my old point-and-shoot camera). It works great for recording people speaking, and sort of works for some insects. BUT . . . it turns out that there is a serious problem that I hadn’t expected. When I later tried to use it to record higher-pitched insect sounds, like crickets, it gave me a big fat nothing. It would reliably pick up children’s voices from clear across the room, but the crickets and dog-day cicadas that I was trying to record were completely undetected.

This doesn’t seem to be a microphone problem – I connected it to an external microphone, and it still couldn’t hear high-pitched sounds. I think what it is doing is filtering out the high frequencies from the signal that it gets from the microphone. For recording speech, this is an advantage; it would not only eliminate a bunch of possible sources of noise, but would also make it possible to greatly increase the recoding duration by reducing the amount of data that would have to be stored per minute (the thing claims to be able to record for 34 hours at the highest-fidelity setting, after all!). Some of the more-expensive voice recorders apparently include high-frequency and low-frequency filtering as an option that you can turn off, but I think the cheap one I have just has the filters on all the time (filtering is not mentioned in the manual or in the specifications). So, I might be able to use it to record lower-pitched insects (like this beetle), but evidently not the higher-pitched majority which are up around 15 – 20 KHz.

Luckily, I didn’t spend much on it. And I actually do occasionally have a use for a human voice recorder, so that’s OK. It’s just that now it looks like if I want to record the local insect songs, I need to find a portable recorder that is designed for music recording, and not for voice recording. And I’m becoming annoyed by the fact that the specification sheets for voice recorders rarely come out and say whether they clip the high frequencies or not. I guess I just have to assume that anything that calls itself a “voice recorder” just isn’t going to work for singing insects, and restrict myself to “music recorders”. Unfortunately, the music recorders seem to all have integrated stereo microphones, which makes them quite a bit more expensive.

[2] When I got the recorder at Wal-Mart last year, I thought it was interesting that, right next to the digital voice recorders, they were still selling cassette tape recorders! The tape recorders for sale had the same exact functionality as the one that my mother bought around 1970, and cost about the same as the digital voice recorders (about $30). I guess this just shows that an obsolete recording format can take a loooooong time to finally die completely. And actually, given my problems with the digital voice recorder not recording high frequencies, I don’t know. Maybe I should just buy the tape recorder and use that to record insect songs instead!

11 Responses
  1. JRR permalink
    August 27, 2011

    Voice recorders definitely have a low pass filter, this allows them to compress voice recordings quite a bit and have them still be intelligible, but as you discovered, pretty much zero out anything above perhaps 8-10KHz, maybe even lower.
    A good, full range digital recorder would be better. I use the Zoom H2 for recordings at church, but it’s > $150. Alesis makes a nearly identical recorder but with a cheaper build for > $50. Go to Newegg and look up the Alesis PalmTrack. It can record up to 48k samples per second and either MP3 with bit rates up to 320 kbps or (better for your purposes) WAV files. The only real downside I’ve seen people complain about is build quality, but you can’t get everything for 50 bucks.
    The Zoom can sample at 96KHz but that’s not really needed unless you’re sampling complex things like orchestras where multiple sound interactions might cause aliasing at lower frequencies.
    These things also have external microphone inputs so it would even be possible to get a tiny microphone even as small as a pinhead, on a wire and be able to put it right up to creatures.

  2. August 27, 2011

    You don’t have to buy a tape recorder: just put out the word on Freecycle that you’d like one that still works. Bet you get a dozen replies; so many families had them back in the day and as the Aged Parents downsize, there are plenty to be had for the asking!

  3. August 27, 2011

    But JRR’s idea is probably better. Be sure to have someone photograph you holding the tiny mike up to the subject of your beetle-on-the-street interview!

  4. August 28, 2011

    I played it backwards and heard subliminal suggestions to go out and buy Pop Tarts. Weird creatures, these beetles.

  5. August 29, 2011

    Yuck! What a weird looking bug!

  6. August 30, 2011

    Thinking it over, if I buy a recorder at all it should be a decent one, and $150 is roughly comparable to a point-and-shoot camera. Since there are several “Zoom” recorders, I’ll have to look them over to see which one actually does what I want.

    I thought for a minute that I had a tape recorder that I could use with my existing external microphone (a pretty high-end one that I got at a steep discount ($10) from American Science and Surplus), but my old boom-box doesn’t have a microphone jack. Come to think of it, my computer has a microphone jack, I could at least test out my parabolic dish setup by pointing it out the window . . .

    And, very funny, KT. Incidentally, how hard is it to play computer sound files backwards? Is there a program to do that?

  7. September 1, 2011

    Tim, I can do that for you if you’d like. I’ve got the full on Adobe Creative Suite and can do it any number of ways. There’s also a very nice program called GoldWave which may have a freeware version to do it. Google it and you’ll see.

  8. Jacob C. permalink
    September 1, 2011

    I hope it isn’t rude to assume you have a PC? This blog post would indicate so, but in the age of smartphones and tablets…

    Most desktop PCs can record from a 1/8 inch input, while often not astounding quality, they do quite well with a decent microphone. Use a 1/8 to 1/4 convertor if needed to plug in your chosen microphone. Audacity is a free (open source) recording program, that can also reverse any recording.

    If you have only laptop PCs you may not have a microphone-in, but may instead have a poor quality integrated microphone, or may have both options.

  9. September 2, 2011

    KT: I appreciate the offer. I don’t actually have a sound file that I want to reverse, it was more a matter of idle curiosity in case it ever came up.

    Jacob C: My laptop does have a microphone port, so I can plug my microphone into it. I’ll check out Audacity, and see what it does, thanks.

    The only problem is that a laptop isn’t that portable. It will be fine for insects that I catch and bring in the house, but for field recordings of katydids and cicadas, I’ll need something more portable.

  10. JRR permalink
    September 3, 2011

    For pretty much anything that you’d ever want to do with an audio file, try Audacity. Free, open source. Does tons of stuff, very comparable to most commercial stuff. I use it a lot and the more I poke around on it the more I’m surprised by what’s in there.

    One thing that you might be interested in, and the Zoom might help with, is investigating the ultrasonic range. For that you’d need a specialty microphone, one that has a frequency response up in the 40-50khz range. If you plug that into a Zoom recorder and boost the sampling up to 96khz, you should then be able to load the resulting WAV file (I wouldn’t do MP3 for this) into Audacity and slow it down to listen. Most recording devices these days won’t sample at over 44khz, and that won’t really do for recording frequencies above about 20khz.

    Todd (you know who I mean) has done some looking into high frequency microphones in his bat research. Mainly for component microphones for his ListenUp device but he may know of stand-alone ones or be able to set you up with one of the component mics attached to a 1/8″ plug that would go into a recorder.

  11. Della3 permalink
    November 7, 2011

    I tried the microphone input on my PC and was thoroughly dissapointed (actually, I wanted to write disgusted). It barely picked up any sound and was very poor quality, even with a good microphone. Perhaps there’s some trick to it that I’m not aware of, or some software that improves the quality. I finally got a high-quality digital recorder. For quick recordings that don’t need to be downloaded to my computer I still use an ordinary tape recorder. I seldom need it, but I’m glad I haven’t thrown it out.

    Tim, I, too am often frustrated at the lack of detail in descriptions and specifications on many products – especially products we buy on the internet. Even the photos are often seriously lacking in quality and detail. If we can’t hold it and touch it, we need lots of photos and specs. Even software can be quite unspecific in the descriptions. It makes me want to shake some people. If we shook enough manufacturers at once, what would it sound like?

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