nature | The Prairie Ecologist

I was trying to pay attention to the tour. We were at the Shaw Nature Reserve for the 2026 Grassland Restoration Workshop and learning about some great prairie and woodland restoration projects. I really was trying to stay tuned in. Unfortunately, I couldn’t stop watching carpenter bees steal nectar from penstemon flowers.

Both the foxglove penstemon (Penstemon digitalis) and the carpenter bees (Xylocopa virginica) were all around us in big numbers. The bees were very active in their visits of flower after flower. Clearly, the nectar was worth acquiring.

If you’re familiar with penstemon flowers, one of their key characteristics is their tubular flowers. I often see pollinators of many kinds flying or squeezing their way into those tubes to get nectar, exiting again with pollen stuck to their bodies. The architecture of the flower is well-adapted to facilitating pollination. Of course, that only works if the pollinators follow the rules.

At first glance, it might look like this carpenter bee is just doing its pollination job. However, you’ll notice the bee is not inside the flower, but on top of it.

What the carpenter bees were doing was landing on top of the flowers and using their mandibles (~teeth) to cut two little slits in the base of each blossom. They’d then stick their tongues through those slits and access the nectar directly. Subsequent thieves visiting the flower used those same access slits and stole more nectar. Those other thieves included lots of carpenter bees, but also some bumble bees and honey bees, who seemed more than willing to use the same shortcut.

Here, you can see the bee’s tongue being inserted into the base of the flower to extract the nectar without doing the flower any good at all.

Here are the slits created by the mandibles of carpenter bees that give them (and other bees) direct access to the nectar inside.

Carpenter bees are known for this behavior, but they’re not the only ones. Bumble bees and honey bees, along with other bee species, sometimes do this as well. In some cases, they’re probably doing it because their body size or tongue length doesn’t give them any other way to get to the nectar. In other cases, I’ve seen some bees going about nectar acquisition legally and others (of the same species) taking shortcuts.

This carpenter bee’s eye contact shows how little shame they have about their larceny.

While half listening to our tour guide, I saw hundreds of penstemon flowers being robbed by dozens of carpenter bees. Bumble bees and honey bees appeared to be following the carpenter bees’ example as well. Not once did I see any pollinator insect go in the front door and pick up/deposit pollen. I’m sure it happened – I just didn’t observe it.

Nectar thievery is common but I don’t know of any examples of plants that are struggling because of it. My guess is that there are enough pollinators playing by the rules that the cheaters don’t have a major impact on seed production, but I’d be interested to hear from anyone who knows differently. Either way, I guess it’s an admirable adaptation on the behalf of the insects and, apparently, a big distraction for tour members who notice it happening around them. Apologies to our tour guide for my inattention.

I don’t have a favorite plant. I don’t even even have a favorite milkweed. Having said that, spider milkweed, aka green milkweed (Asclepias viridis) is right up there. It has gorgeous flowers, but they aren’t particularly flashy. Their yellow-green color doesn’t stand out from a distance like the orange of butterfly milkweed or the pinks/purples displayed by many taller milkweeds. Speaking of height, spider milkweed has large flowers and a lot of biomass, but it keeps itself relatively close to the ground. It comes across as quietly self-confident. No reason to show off when you know you’re spectacular and have nothing to prove.

This spider milkweed plant is blooming in an area where cattle were grazing just a week ago. All the common milkweed in the same area is re-growing from being nipped off.

Spider milkweed is also a tough plant. It resists grazing from cattle, as opposed to species like common and showy milkweed, which cattle gobble like cherry pie (bison like them too). To clarify, I mean cattle eat common milkweed like I eat cherry pie. I don’t know if cattle like cherry pie (I don’t know if bison do either).

At our family prairie, where I took all the photos for this post, spider milkweed is blooming just as prolifically where last year’s grazing was intense (and season-long) as where there was no grazing at all. It doesn’t seem to be more abundant or florific after grazing like some opportunistic plants (hoary vervain, yarrow, etc.). However, it also doesn’t seem suppressed by the competition from ungrazed plants like vervain and yarrow are. And no, florific isn’t a real word. Floriferous is, though. Weird.

I saw lots of pollinators feeding on the nectar of spider milkweed last week, especially bees and flies. I didn’t manage to get a photo of any of the many bumble bees I saw, but I did track down a metallic green sweat bee, though I had to be particularly stealthy to make it happen. Much easier to photograph were the hundreds of tiny flies clustered on the blossoms. Wow, there were a lot of flies.

I’m not kidding about the flies. They were swarming over a lot of the flowers like the flowers were made of cherry pie (I’m just assuming all flies like cherry pie – who doesn’t like cherry pie??)

And, of course, because there were lots of flies, there were spiders to catch them. As the old saying goes, you can catch a lot of flies with honey, but spiders don’t make honey. I don’t think spider milkweed is named for the abundance of arachnids it attracts but I’m not saying it wasn’t.

I only found one monarch caterpillar on the 10-12 spider milkweed plants I examined, but there could have been more. I wasn’t looking at the underside of all the leaves. The one caterpillar I did see was sitting right on top of a leaf and may very well have been the victim of a parasitoid. I don’t want to speak badly of anyone, but this caterpillar just didn’t quite look right. It was moving around, but its antennae were droopy and it didn’t seem to be eating. Did that make it easier to photograph? Yes, of course. Is it annoying when someone asks and answers their own questions? Who’s to say?

Spider milkweed is only one of 17 milkweed species we have in Nebraska. Over the course of the couple hours I was at our family prairie last week, I came across seven species, which was gratifying. Those included spider, green (aka, green comet), narrowleaf, common, whorled, butterfly, and wooly milkweeds. The wooly milkweed was a particular highlight because it’s the first time I’ve seen it at our prairie. None of the three plants I saw were blooming this year, but now that I know where they are, I’ll keep a closer eye on them in the future.

The plant community at our family prairie is still a work in progress and the diversity and abundance of flowers is not what I’d like. I see progress each year, but it’s hard to be patient with the speed of change. When it comes to spider milkweed, though, I feel very fortunate to see a lot of it and that it seems to be growing even more abundant over time.

I could sure eat some cherry pie right now.

The Prairie Ecologist

Essays, photos, and discussion about prairie ecology, restoration, and management

Tag Archives: nature

Nectar Thieves

Photos of the Week – June 7, 2026