Bugged by Surprises
Nature, white in flower and noisy as heck, never ceases to amaze.
The little yucca that somehow manages to grow in the narrow pavement-free swath between the patio and the barbecue-grill area suddenly decided to flower this year. I'd hardly even been aware before that it was there. Its spindly green spikes of leaves barely stood out against the low stone wall that pickets our barbecue area, or from the surrounding camouflage of—let's be honest—weeds.
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But nature, as I'm continually reminded, is full of surprises. So one day we looked out and there it was: an asparagus-like stalk jutting from the core of this hitherto overlooked yucca.
Once the yucca opted to stand out from the crowd, it settled for no half-measures. You could almost hear the thing grow. I'd mentally mark its progress when sitting outside after supper—yup, almost to the top of the hook that holds a hummingbird feeder—and inevitably be surprised the following evening. Now the stalk had surged past the ground-mounted feeder entirely and was stretching toward the ramada that shades my sprawling collection of grills, smokers and related apparatus. (Each grill has its own specialized uses, of course. Would you ask a surgeon, "Gee, do you really need all those different scalpels?") A day later, the stalk waved in the wind from its new elevation, haughtily looking down on the ramada.
Barely had the yucca established that it was the tallest thing in the neighborhood before the top end of the stalk began to thicken in preparation for blooming. I love the large but delicate petals of the yucca flowers, as white as eggshells against the vivid blue of the New Mexican sky. Up close, in the right light, the flowers can also seem faintly greenish, as though the blooms were blushing—but chlorophyll green, of course, instead of blood red.
Other yuccas around the yard have been busily getting ready to bloom all this time, too, naturally. One yucca on my way to the mailbox has been particularly notable, both for the height of its promised flowers and for its solitary stance among the scrub oaks and low-crawling weeds. But none has gone quite so startlingly from near-invisibility to instant, waving-in-the-breeze prominence as that wedged-in backyard specimen.
Take nothing for granted, the yucca seems to whisper as the June winds—also a bit of a surprise (shouldn't they have settled down by now?)—rustle its spiny fronds. Expect the unexpected.
Nature loves to throw us a curve, every now and then, just to keep us on our toes. Getting too comfy down there on the Gulf Coast? Bam! comes Hurricane Katrina. How about last month's tornadoes near, of all places, Santa Fe? Or the surprises can be pleasant, like our yucca's sudden flowering or, two springs ago, the unanticipated painting of the Bootheel with a profusion of yellow poppies.
Also unexpected this month has been the near-deafening song of an unusually large crop of cicadas. I'd seen reports about the cicada invasions expected in the Midwest, but we've had the bugs in earnest only once since we've lived here, so I dismissed it as something to watch on the nightly news. Indeed, friends who live closer into town tell us they've had no cicadas at all.
While hardly the squishy, creepy-crawly army endured in places like Chicago and Cincinnati, we've had a platoon or two of cicadas here. Enough, at any rate, for some surprising sights: The other evening, a cottontail rabbit hippity-hopped into the midst of a cicada choir and sent them flying—like the mousetraps and ping pong balls that educational films used to employ to demonstrate an atomic chain reaction.
And then there's the noise. (There it goes again, even as I type those words!) The high-pitched, electric chittering sounds something like a rattlesnake's warning crossed with a Weed-Whacker, crossed with the sizzle of water hitting hot oil—but goes on far longer than these sounds and then, just when you think it's finally ceased, starts up again.
It's the sheer volume that amazes. A cicada can hum louder than a lawn mower—90-plus decibels—according to one news report of the havoc the bugs have been wreaking out east. (Plan a June outdoor wedding? Think again.) For comparison, many cities outlaw noise greater than 70 decibels in residential neighborhoods—though just try ticketing a cicada. Some large species such as the Greengrocer or Yellow Monday and the Double Drummer cicada produce a racket in excess of 120 decibels at close range, said to be approaching the pain threshold of the human ear. An NPR story added that one variety of katydid, a relative of the cicada, can shatter window glass with its mating call.
Mating is what it's all about—not surprisingly. When cicadas hatch after up to 17 boring years in the ground, their sole job is to mate and then die. So male cicadas sing frantically to attract the attention of a female, not unlike teenaged boys cruising with their car stereos cranked to ear-splitting levels.
The males possess two special noisemaking organs called "tymbals" on either side of their abdomen. By buckling muscles attached to each tymbal—like denting a soda can—the cicada shoots a pulse of sound into an air sac in the abdomen. The pressure of the tymbal pulse, according to a Scientific American article, is "roughly equivalent to that generated by a grenade exploding one meter away."
Female cicadas are not similarly endowed. So if you annoy a male cicada—as my wife has become fond of doing, a sort of revenge for their swooping at her while she tries to do yard work—it emits an aggravated chittering as it flies to safety. Pester a female and it silently sulks off.
Both male and female cicadas have ears—so the females can hear the mating sounds, which are unique to each species—but only males also use their ears, which are on the abdomen, as amplifiers. Scientists have recently discovered that these eardrums boost the sound originally emitted by the bug's tymbals to be 20 times louder. Lucky us.
Aren't the bugs bothered by their own raucous mating calls? Once again, nature amazes: The males can crease their ear membranes, called tympana, so they don't deafen themselves.
But back to mating, or at any rate the propagation of the species. That's what it's all about for the yucca, too, which has to reach about five years old or more before it's mature enough to send out those surprising flowering spikes.
Why, though, bother to stretch so high toward the sky before blooming? I'm no evolutionary biologist, but after giving our backyard yucca and its airy aspirations some thought, I suspect height must help scatter the seeds—which, after all, are the whole point of flowering—more widely. Yuccas produce capsule-like fruits, which eventually split open to reveal stacks of black, flattened seeds. The wild New Mexico winds can more easily shake loose the higher-placed seeds and carry them farther and wider before they flutter to the ground.
Here again, though, if you poke into yucca biology a bit more closely, nature serves up another surprise. All yucca species have what biologists call "an intimate mutualistic association" with tiny yucca moths. According to the Desert Ecology Web site, after mating, the female moth deposits her eggs in the ovary at the base of the flower. Then the moth flies around and collects pollen from other flowers, placing this pollen ball in a special depression in the stigma of the flower, to insure that the yucca flower is fertilized. This system is so precise that only yucca moths can pollinate these plants, and different yucca species are pollinated by different, specialized yucca moths. Yuccas grown in regions lacking the right moth produce seeds only by hand-pollinating.
What's in it for the moth? As the yucca's fruit capsules ripen, the yucca moth's eggs hatch and the larvae feed on the seeds. The moth larvae eat through some of the seed columns and fall to the ground. Much like the cicada—only faster and with less future prospect of noise—the moth then pupates in the soil, so a new generation emerges the next year to enact this mutually beneficial arrangement all over again.
The closer you investigate, the more surprising nature seems. Not merely annoying, the cicadas have evolved a noisemaking (and ear-muffling) system that any human teenager would envy. The yucca that surprised me by bursting skyward exists only because of an even more amazing partnership with another bug. No tiny moth, no papery white flowers.
We think we're pretty amazing ourselves, with our computers and swamp coolers, our barbecue grills and atomic chain reactions. But an earful from a cicada or the explosive blooming of a yucca can provide a proper dose of humility. Have you ever come up with anything as, well, cool as that?
If anybody out there develops a cicada silencer, though, feel free to surprise me.
David A. Fryxell is editor of Desert Exposure.