Summer has officially arrived in southern Arizona, even if the calendar says it’s still a couple of weeks off. Daytime temperatures in Tucson have exceeded 100 Fahrenheit for the last several days, and are expected to stay above 100 for the foreseeable future.
One of the few things that makes this kind of heat tolerable is the dryness of the air. The humidity is below 20% and occasionally below 5%, making evaporation a very efficient mode of cooling. Many homes in this area are cooled by evaporative (“swamp”) coolers for at least part of the summer. In mid- to late-summer, the monsoon rains arrive from Mexico, and the increase in humidity makes swamp coolers much less effective, so some people switch to air conditioning at that point.
My house, in the hills east of Tucson, is cooled by a swamp cooler. The nighttime temps average about 10 degrees cooler than in Tucson, so I’m able to get some extra cooling at night. For some reason my swamp cooler, which is on my roof, has been giving me all kinds of grief this year. Leaks and clogs and bearings have required seemingly endless trips up to the roof, sometimes in the middle of the night, sometimes in the late morning when the shingles on the roof are searingly hot. This morning was another one of those mornings. Sweating buckets while replacing hoses and valves and lubing up the bearings. Yes, those are things that should have been done last month when it was much cooler. But when I ran the cooler through its pre-season check, everything seemed good to go.
This morning, after I finished the latest round of swamp cooler whack-a-mole and was descending the ladder with fingers crossed that it would work, I heard the first cicadas of the season. Apache cicadas (Diceroprocta apache) like it hot. After spending several years underground as nymphs, feeding on liquid from the roots of trees, they emerge, molt into their adult form and settle into the serious business of creating the next generation. Males begin loudly “singing” by rapidly clicking special tymbals on their abdomens. Their abdomens also act as resonating chambers, amplifying the sounds to levels that can actually damage human hearing if close enough. Cicadas also like to sing in choruses, which may further amplifies the sound. In addition to potentially attracting female cicadas from further afield, I wonder if this impressive din might also serve as a predator deterrent. Apache cicadas stagger generations, so that cicadas are heard here every year, not in 13 or 17 year cycles like in other parts of the US.
Now you might think that I just made a really awkward transition from swamp coolers to cicadas, but actually that was an artfully crafted segue. You see, Apache cicadas (and some other species of cicadas, too) have their own built-in swamp coolers that allow them to tolerate the heat of midday in the desert. In other words, they sweat. Rapidly moving their abdomens in and out generates a lot of heat, so sweating helps keep them from spontaneously combusting, It’s interesting to note that Apache cicadas go quiet about the time the monsoons start. Guess they can’t handle the increase in humidity, either.
Here is a cicada chorus I recorded in my front yard last summer. If you listen on headphones or good stereo speakers, you can hear the chorus moving through the tree tops. This is from individuals in different trees singing at different times, giving the impression that the sound is moving.
The cicada chorus, even when its loud enough that it makes my head feel like its going to explode, is one of those phenomena that make me pause with wonder. How can a little bug create so much noise? The more time I spend recording, the more I realize how important insect noises are to our natural soundscapes.
What are your favorite insect sounds?
Photo copyright Steev Hise, 2006, under Creative Commons license.
Recorded using a Sony PCM-M10 and Audio-Technica AT2022 mic.
It looks like a synth sound, nice. I’m great fan of crickets and bees, just the sound not the bites 😉
Insects sure add a lot of dimension to the soundscape, don’t they?
And indeed, they can really get whining here, too! I hadn’t put the softer sound (yes, like tiny castinets) together with emergence—I’d thought of it as just some other behavioral bit that was more subtly audible—but now that you mention it, I can easily imagine that they were freshly emerged. These were definitely out of their shells, but perhaps not for long. Great!
I hadn’t considered the castanet sound relating to the newly emerged cicadas either. I checked with an entomologist friend who said that insects usually don’t start calling until their exoskeletons have hardened, but admitted he doesn’t know that much about cicadas. I just assumed I was hearing two species, a higher frequency buzz and the lower frequency clicks. Obviously, I don’t know much about cicadas, either, but I don’t let that keep me from appreciating the sound!
I also love the subtle clicking sound of cicadas in our scrubby piñon pines here in northern NM. It took a few years here before I discovered it; you have to walk right into the embrace of the tree to really hear it, then it’s all around!
Great description! Now that I’m really listening for them, I’m amazed at how many different sounds cicadas make. I was just on the north side of the Gila, and some cicadas there were just emerging that made a lovely castanet sound. On the other hand, I’ve been in pine-oak habitats where the cicadas are really overwhelming.