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Good Natured: Grapevine beetles – what's not to love?

Published: Friday, Aug. 15, 2014 10:32 p.m. CST
Caption
(Photo provided)
These male grapevine beetles (Pelidnota punctata), shown here feeding on their namesake plant, bear little resemblance to what they looked like as larvae.

Ah, babies. Dontcha just love ’em?

Over the course of a year, hundreds of babies, and their parents (or grandparents), come through the doors at Hickory Knolls. We try, as often as possible, to engage the adults in conversation about their little darlings: What’s his/her name? How old? Does she/he have a favorite animal?

Invariably over the course of these chats, we hear how it is that the wee one resembles one parent (or grandparent) or the other: “She’s going to be tall, just like her mother.” “She has her daddy’s eyes.” “He’s got red hair, just like my dad did.”

But then there are those tots who, frankly, defy comparison. Like the bucket of babies I was given by my friend Joan.

Some of you may remember, a few months ago Joan – as in Joan Kramer, the wizard behind the beauty in the Native Plant Garden at the Pottawatomie Community Center – was preparing for spring by spreading hardwood mulch over the plant beds she’d raked. But her seasonal ritual was interrupted when she came across not one or two, but somewhere in the neighborhood of 40 or so plump, juicy-looking grubs.

The whole operation ground to a halt while she shoveled and scraped the youngsters out of the mulch pile and placed them, one scoop at a time, into a coffee can. Later on, they were transferred into a bucket – a bucket I truly was overjoyed to receive.

The only question was, “Whose babies are these?”

The thing about grubs (and caterpillars, maggots and other immature insects, or larvae) is that they bear little resemblance to either Mom or Dad. With grubs, a.k.a. baby scarab beetles, only a few bits of their “baby parts” remain after they pupate and become adults. Their soft, white bodies change form, heads change shape, wings sprout ...

Now, some entomologists – especially coleopterists, those dedicated folks that specialize in beetles – can look at a grub’s anal slit, its rastral pattern (the arrangement of tiny spines or hairs on the last abdominal segment) and maybe a few other characteristics and, boom, identify it to genus or species.

The rest of us aren’t so lucky. We need to be a little more patient, and wait until the larvae mature and pupate – a period of time that can take weeks, months or even years, depending on species.

Luckily, in the case of these grubs, no one was in a huge hurry to find out exactly what they were. What’s more, I had a spare clay flower pot (thanks Mom and Dad!) and some space on my kitchen counter to let the process play out in its own due time.

(Incidentally, the tendency to allow beetles to pupate on the kitchen counter is something I did not inherit from either of my dear, tolerant parents.)

The month of April passed uneventfully. I watered the mulch occasionally, keeping the grubs’ environment just barely moist, and watched for escapees (of which, thankfully there were none).

May was quiet, too although as the month progressed, I noticed more and more other types of beetles (most likely “May” beetles, or chafers) coming to the porch light at night. Occasionally, one or more of these guys would sneak in when I’d open that door, much to the delight of my cat Jimmy.

One evening though, as I listened to him crunch on yet another six-legged morsel just inside the back door, I had a horrifying thought. “What if he’s eating MY beetles?”

A quick sprint around the room and a brief but intense skirmish later, I had Jimmy in my arms and my fingers in his mouth, trying to salvage what I could of his late-night snack. Alas, he had just swallowed the last bits of the crunchy prey.

Insulted at my rude intrusion, Jimmy leaped away and sauntered – as only cats can – -back to his spot by the door. Meanwhile, I headed for the clay pot on the kitchen counter. I scanned the surface of the mulch for signs of exit holes and saw none.

Phew!

With one disaster averted, I wasn’t about to risk another. So into a glass aquarium the plant pot went. I tipped it on its side, so that the mulch spilled out a bit, and misted the surface again to preserve the lightly moist environment in the “nursery.”

As the calendar pages flipped from May to June, I began to wonder if maybe the babies were of a sort that have a multiple-year life cycle. Then, around June 10, I saw it. Or him, as I realized later. A large beetle, about the size of a queen-size olive, was poking its way around the bottom of the aquarium.

Now, I don’t want to sound haughty or anything, but this was one beautiful beetle. Orangish, almost terracotta on top, it had a dark head and legs that – gasp – shined an iridescent green when the sunlight hit them. Widely spaced spots dotted the edges of his elytra, or forewings – the part we think of as a beetle’s “shell.”

As I admired the stunning creature before me, I realized that it was unlike any beetle I’d ever seen. It most certainly was not Osmoderma, the genus I’d guessed when I first adopted the grubs.

So off to BugGuide.net I went, and used the website’s “Browse” feature to quickly flip through North American scarab beetle groups. Clicking through the various options, it didn’t take long to arrive at genus Pelidnota, and then species punctata – a critter otherwise known as the grapevine beetle.

Although related to other beetles with less-than-stellar reputations, adult P. punctata generally are not found in numbers large enough to cause damage to their host plant, which is – go figure – Vitis spp., or grapevines. The beetles also will munch on Virginia creeper (Parthenocissus quinquefolia), according to other references.

Eggs are laid in rotting wood of various hardwood trees, including maples, hackberries, walnuts, apples, oaks and elms. When the larvae emerge, they begin feeding on the dead wood, hastening the decomposition process and returning all the good things that once made that tree back into soil, from which new trees can grow.

As more and more grapevine beetles began emerging from the mulch in my kitchen, I noticed that not all were orange. Some were lighter, almost khaki, in color, and larger, too. These were the females.

Two months into this grub-incubation experiment, I’ve got about two dozen beetles living in the large aquarium in my kitchen. Males outnumber females roughly 2-to-1. Each day I feed them fresh grape leaves, clipped from the wild vines that encircle my yard. And each night the beetles emerge to feed and carry on certain other necessary activities.

I’m hopeful the females will soon start laying eggs in the ample mulch that still forms the substrate in the tank and that, when they hatch, the cycle will start anew. I’d like the chance to once again become familiar with the features that identify the grubs – this time knowing what the result will be.

They may not be tall like their mother, or have their father’s eyes, but these babies will nonetheless carry on the traits of the generations before them: Hardworking decomposers, carrying on the important business of nutrient recycling.

What’s not to love?

• Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346 or potto@stcparks.org.

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