Posts Tagged Megachile sculpturalis

Farewell Summer!

Pearl Crescent enjoying a Coreopsis bloom in mid-June

My apologies for my prolonged absence. It’s been a long, strange summer — for most of us, I imagine. I’m planning on being here more reliably henceforth.

As you likely know, today is the last full day of astronomical summer. Finally in my yard today, we are getting measurable rain — a weather phenomenon that has been absent for over two months. Folks 30 miles to my east have experienced flash floods more than once during that time. My yard however, has been a dust bowl. You know it’s bad when tree leaves hang limp even in the early morning. It hurt me to walk around and see them suffering.

Today, however, perhaps to usher in tomorrow’s autumnal equinox, our skies are finally dark. Occasional showers have reawakened the long-dormant rain gauge. I imagine plants and animals alike are reveling in the water as much as I am.

This summer was tough on native butterflies. Posters on the local email butterfly group I follow have been lamenting all summer on the low numbers of lepidopterans observed. They’ve also commented on the low numbers of spiders. I’ve noticed both of these phenomena in my yard too. There was a spell of about six weeks when the only butterflies I saw were a couple of Pearl Crescent butterflies like the one above.

Native solitary bee numbers were variable. For the first time in forever, I had both American bumblebees and brown-belted bumblebees abundantly present on my flowers. Solitary wasps were also present in great numbers, and I think this may have been bad news for my caterpillars. Every time I’d spot a Monarch caterpillar or a black swallowtail caterpillar on my plants, the next day, it would be gone. Wasps were everywhere, searching every leaf, so I suspect they were catching the caterpillars to bury in their nest tunnels to feed their hatchlings. It could have been birds too. They were here in relatively normal numbers this summer, I’m happy to report.

Giant Resin Bee on Common Milkweed inflorescence

Besides the drought, the worst news of the summer for my local Green World was the appearance of a new invasive exotic species. Giant Resin Bee, also called Sculptured Resin Bee (Megachile sculpturalis) is native to Eastern Asia. It was apparently introduced to the US in the 1990s, and showed up in significant numbers at my house this summer. It’s a kind of carpenter bee, but unlike our native carpenter bees, it doesn’t create its own nesting tunnels. Instead, it appropriates tunnels belonging to other insects, especially our native carpenter bees. The link above provides all the information you need to know about this recent invader.

I noticed these bees about mid-June when they were all over my blooming Common Milkweed and Narrow-leaved Mountain Mints. These are big bully bees. They would land on flowers hard, shoving all native pollinators aside as they claimed nectar and pollen for themselves.

I took a photo and posted it to my iNaturalist account in hopes of learning the identity of what was at that point a mystery bee. I got an answer very quickly. The entomologists on iNaturalist must have been watching for reports. In fact, just a few days after my Giant Resin Bee photo was identified, I got an email via iNaturalist from an entomologist in Vienna, Austria working on her Ph.D. on this species. She is doing DNA analysis on this species collected from all the parts of the world to which it has spread. Her goal is to determine migration patterns of the bees, based on DNA analyses of populations. She asked me if I would be willing to collect bees, freeze them to preserve their DNA, then give them to a colleague in the US who would collect them and ship them to her for analysis. Of course, I said yes — citizen science for the win!

These two invaders chased off every other pollinator that had been enjoying the milkweed flowers.

I spent a number of hours patrolling my flowers to collect as many bees as I could for the study. I became adept at spotting the males; they have a characteristic yellow “mustache.” There’s a good photo of this feature in the link above. The females are bigger, less numerous (thank goodness), and showed up about a week after the males appeared, which, the entomologist from Vienna told me, is normal.

All told, I collected 40 Giant Resin Bees, mostly males, which completely flabbergasted Julia (the entomologist). She had never heard of anyone seeing, much less collecting, that many bees. And I think, alas, I know why. There’s one last detail I haven’t told you yet.

Giant Resin Bees evolved in the same part of the world as kudzu, and it is what is called an “effective pollinator” of that plant, which means that when Giant Resin Bees visit kudzu flowers, the flowers get pollinated and set seed. This is a nightmare scenario for those of us living in the Southeastern United States. Up to now, kudzu — although a notorious invasive species — has not been as big a threat to native ecosystems as many other non-native invaders, because it only spread vegetatively. Our native pollinators were not effectively able to pollinate kudzu flowers because they didn’t evolve with them, so kudzu was only rarely setting seed. Thus, all we have had to worry about — as if that wasn’t enough — is the terrifying vegetative growth rate of kudzu, which grows several feet per day during our growing season. But if it starts setting seed reliably, and those seeds spread out via animals and/or natural weather processes and germinate, the potential for kudzu world domination explodes!

When I learned of the Giant Resin Bee-kudzu link, I wrote my favorite local expert, Johnny Randall, Director of Conservation Programs at the North Carolina Botanical Garden, to ask him how worried I should be about kudzu world domination. He told me that if the Giant Resin Bee continues to spread and pollinate kudzu, the only thing standing between us and a Kudzu Apocalypse is a native weevil with a fondness for eating kudzu seeds. I never thought I’d be praying on behalf of a native weevil, but this kudzu-seed-eater has my full support!

Why did I collect so many Giant Resin Bees on my kudzu-free <knock wood> five acres? Because my “neighbor” across the road from me permits kudzu to roam freely over most of his multi-acre property. If not for the busy road that separates us, kudzu vines would have certainly crossed over to our yard years ago. My guess is that kudzu flowers drew the Giant Resin Bees to my neighbor’s yard, then some flew across the road and discovered the abundant native flowers blooming in my gardens.

You’ll see in the link further up that local extension agents are asking folks to report sitings of this bee. They don’t really have a handle on how many are here in the Southeast. I’m betting that if you live near kudzu like I do, these bees will be on a flower near you next June. Be sure to report them if you see them. Meanwhile, I’ve still got 40 frozen Giant Resin Bees in our freezer awaiting pickup by a local entomologist.

 

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