Wild Ideas: Golden days offer bug buffet

After suffering through the dank, oppressive weather left over from Hurricane Isaac in early September, the month showed us its best side: The air turned drier, the sun was bright but the temperature stayed down, the golden blossoms of late summer were everywhere and bugs were swarming to them.

With the primrose blossoms all but gone now, the more vibrant yellow of goldenrod has taken center stage outside my bedroom window. There are several species, and even experts have trouble sorting them out, so I won’t try, but one decided that my compost pile was a great place to root. It was nice to now be greeted at dawn with clouds of bright yellow waving in the early morning sunlight.

Lots of ailanthus webworm moths (Atteva aurea) feed on goldenrod. Photo by Pam Owen.
Lots of ailanthus webworm moths (Atteva aurea) feed on goldenrod. Photo by Pam Owen.

Before it blooms, goldenrod can look unhealthy, with its tops limp and even curled. I keep thinking it’s infested with some kind of wilt or insect pest, but it always snaps to attention once the buds start growing. Then, by late summer, it bursts into clouds of gold, joining the other yellow blooms that dominate this time of year here in the hollow, from the brilliant narrow-leafed sunflower  and wingstem (aka yellow ironweed) to the more subtle spotted jewelweed.

I love the brilliant color and graceful shape of goldenrod blossoms, but I’d never examined them closely until this year. In the clump growing in my compost, I discovered a diverse ecosystem of insects. One stood out more than the others and was new to me. Vibrant yellow and black, it resembled a large yellow jacket.

However, the shape of this insect’s head and body (no tiny wasp waist) and its style of rambling on the plant first tipped me off that it might be a mimic instead. Such mimicry of more dangerous species is common among insects. When this bug took flight, it revealed its true self. It looked slow and clumsy, showing wings that were thicker and more opaque than those of wasps – and the takeoff style was distinctly beetle-like.

Now that I’d figured out what I was looking at was a beetle, I had to determine what species, so I took out my numerous bug references. It didn’t take long to track down this wasp lookalike, which measured about three-quarters of an inch. It was a locust borer (Megacyllene robiniae), in the longhorn beetle family, which is named for the long antennae of the species in it.

An adult locust borer, a native mimic, feasts on goldenrod pollen.
An adult locust borer, a native mimic, feasts on goldenrod pollen.

As its name implies, the locust borer bores into native black locust trees in the fall and related cultivars to plant its eggs. The larvae hatch out in the spring and feed on the woody parts of the trees. While the larvae can damage, even kill, their host, the upside is that this beetle is a native species and therefore has native predators, including wheel bugs (Arilus cristatus) and woodpeckers. Adult locust borers feed on goldenrod pollen.

We tend to think of spring as the primary breeding season for wildlife, but many species breed in late summer and early fall, as the Locust Borers on my patch of goldenrod have demonstrated. They seem to alternate between chowing down on goldenrod pollen and romancing the opposite sex.

Many other species with warm colors – from yellow to orange to brown, often alternating with black – are also drawn to the goldenrod, some to eat the pollen and some to feed on those who are eating it. I spotted Asian and native ladybugs, a black stinkbug, a margined leatherwing beetle, lots of non-native ailanthus moths, a red-spotted purple butterfly, an ant-like flower beetle, red and paper wasps and several species of flies and bees, among others. This tiny universe provides a good opportunity for learning about these insects – and it’s great entertainment.

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Pam Owen
About Pam Owen 275 Articles
Writer, editor, photographer, and passionate nature conservationist living in Rappahannock County, in the Blue Ridge Mountains of Virginia. Two favorite quotes: By E.O. Wilson, who coined the term "biodiversity," "Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction”; by Douglas Adams, “I love deadlines. I love the whooshing sound they make as they pass by.”