Innovation Park’s Longhorn Bee Nest Metropolis

2K

Sometimes I ask myself: why do I keep finding interesting bees and bee activity? Here’s an ugly secret I am hesitant to share: the rare bees I have found in the Munson Sandhills have been right along the trail. This is a trail minutes from Tallahassee, not in the remote heart of the Apalachicola National Forest. I have seen my share of bee drama in the garden, but that’s no shock. I plant native plants and I watch them. And now this latest find here in Innovation Park. The real question is: why wasn’t I seeing interesting bees all along?

I didn’t always notice bees, but then, I wasn’t always paying attention. Since I started really looking at insects a few years ago, every small movement catches my eye. What I’ve learned is that insects are more present than I had previously noticed. North Florida is a plant-rich place, with a high diversity of plant species. Consequently, this is an insect-rich place as well. All we have to do is look.

This is a story about a metropolis of longhorn bee nests near a sidewalk I’ve walked for years. Could a congregation this large be new? And, if not, how had I missed it all these years?

The mystery of the concave longhorn-cuckoo bee

The story starts last fall, with a single longhorn bee that I had noticed on Bidens alba flowers next to WFSU. I walked past it for a few days, and then it was gone. I noticed it, but didn’t pay it much mind.

A short while later, I found another bee lingering near a hole in the earth. Now I stopped, and photographed it. I had never seen the bee before, and I always like meeting a new bee. It was an easy match for iNaturalist: the concave longhorn-cuckoo bee (Triepeolus concavus).

Cuckoo bees are kleptoparasites, and they’re specialists. Kleptoparasites are bees that don’t build their own nests. Instead, they lay their eggs in the nests of other bees. Cuckoo bees usually specialize in a species or group of related species of bees, and Triepeolus concavus was known as a specialist of sunflower longhorn bees (Epimelissodes obliqua). The nearest iNaturalist observation for that bee was near Thomasville, Georgia. The only two Florida observations were 100 miles in either direction, but Tallahassee lay at the center of those and the Thomasville sightings.

So, here’s a kleptoparasite that specializes in a bee that may or may not be here, and without which it could not survive. It was a mystery, and one that would have to wait a year.

September/ October longhorn season

Many bee species only fly for a few weeks. Short-flying species tend to fly towards the beginning or end of the year. By year, I mean the year of flowers, which in north Florida is longer than other states: roughly February through November. These are times when there is less competition from other bees, many of which start to wind down for the year in October. I also wonder if there is a connection to fire. In Dr. Jean Huffman’s research into longleaf pine tree rings, she found that, historically, wildfires burned almost every year in Florida, typically between May and July.

One mid-September day, I walked by the Bidens alba flowers by the station and found several longhorn bees – and one concave longhorn-cuckoo. Cuckoo bees lay their eggs in a few cells of a nest, and their larvae are equipped to kill the egg or larvae of its host species, and eat the pollen left there by the host’s mother. Cuckoos won’t replace more than a few bees in a nest. After all, if they eliminate their hosts species, who will collect pollen and build nests for their offspring?

The bees all hatch and emerge together, and the cuckoo bees never stray far from their hosts. I took photos as best I could; the longhorns never stayed on a flower for long. I uploaded the photos to iNaturalist and, then, nothing.

Many longhorns in the Melissodes and Epimelissodes genera (plural of genus) look alike. Almost identical to the naked eye. If your camera doesn’t capture a certain part of the bee’s body in detail, neither the app nor the bee researchers reviewing will choose a specific species.

It’s a mystery that needed more photos to solve, but then the FSU Grounds Crew weed-whacked the flowers.

Longhorn bee city

To be fair, the flowers had expanded into a nearby picnic table. I’m not sure where those bees went, but that didn’t bother me. WFSU is located at the edge of Innovation Park, home to FSU/ FAMU Engineering School and the National High Magnetic Field Laboratory. My daily walk takes me by the engineering school, where, the day before the weed-whacking, I found what looked like a swarm of yellowjackets.

The swarm was right by the sidewalk – uncomfortably close. And yet, I was curious.

I caught a glimpse of a few individuals, and saw they weren’t yellowjackets. In fact, they looked a lot like the longhorn bees closer to the station. These are solitary nesters, and so I walked slowly among them. A few bounced off me, but didn’t sting. As opposed to social bees and wasps, such as honeybees, bumblebees, and yellowjackets, solitary nesters are not aggressive. They are single parents. Unless I went out of my way to make them feel threatened, they wouldn’t risk being lost to their offspring.

I also found a few concave longhorn-cuckoo bees among them, wandering in the grass near the longhorn nests.

Here was an opportunity to watch a congregation of nests. It was also a chance to observe kleptoparasites in action.

A congregation of solitary nests

Since seeing that cuckoo bee last fall, I had read a few papers on longhorn nesting. I was looking for information on cuckoo bees, which means also learning about their hosts.

Multiple longhorn females might share a nest entrance, which keeps bees flying in and out of an opening. This makes it harder for predators or parasites to go after their larvae. The individual nests branch off from the main tunnel.

The bees had made dozens of nests around utility boxes, and under a water main hatch. I occasionally saw bees crawl under the grass, so there were a few nests I couldn’t see as easily. Solitary nesters sometimes group their nests together, but only tend to their own offspring. Compare this to honey bees, where a queen births all of the bees in a colony, and worker bees gather pollen and tend to their larval siblings.

These longhorns must just have emerged, and the first order of business was mating. Two bees would collide, and soon several other bees were piling on. Longhorns reuse and expand their birth nests, so they mate, gather pollen, and return here to fill cells with pollen and eggs.

A positive iNaturalist ID: sandhills longhorn bee

One of the papers I read on longhorn nests found something new about Triepeolus concavus. Researchers at the University of Florida found a congregation of sandhills longhorn bees in one of their agricultural fields. Along with the longhorns, they found several concave longhorn-cuckoos. The paper was published earlier this year.

In my earlier research, I saw that the association between sunflower longhorns and concave longhorn-cuckoos dated back to a 1928 study. An entomologist had dug up over 100 sunflower bee cocoons, and found a concave longhorn-cuckoo inside of one. The researcher admitted that the cocoons had been damaged during excavation. Up to thirty other cocoons had what appeared to be larvae in the Triepeolus genus, but they were too damaged to identify the species. This is the only known association between the two bees.

Now, UF researchers have made a second association for this cuckoo bee.

I uploaded photos of the longhorns at this nest and received an identification of sandhills longhorn bee. You have to be careful about iNaturalist identifications, even from researchers. The most definitive way to distinguish between similar-looking insect species is to capture and examine them. This sometimes involves a microscope, or dissection.

Still, sandhills longhorn bees are common in the area, and researchers have already linked the species to concave longhorn-cuckoo bees.

Concave longhorn-cuckoos begin to infiltrate nests

As I write this, the area around the nests is less active. The bees have mated, and are now more focused on finding nectar. With the longhorns spread out to find food for their grubs, the cuckoos are emboldened.

Bees are born alongside their kleptoparasites, if they have them. Does a longhorn bee recognize this bee as a threat to its offspring?

At first, I thought this was a defensive tackling. But this is a male. Male longhorns typically have longer antennae, and don’t have scopae on their hind legs to collect pollen. I think he was trying to mate with her.

Eventually, the coast is clear, and she enters. She doesn’t stay in long; she has evolved to enter, lay eggs quickly, and leave before the host bee returns.

Still much to learn

The authors of the UF paper observed the longhorn nests, but did not excavate them. I had read about the excavations of other longhorn species’ nests, and it is slow, delicate work. The tunnels are less than a centimeter wide; to map them and their branches without losing them to a cave in takes time. There’s also the handling of the larvae and cocoons.

And then, of course, to excavate a nest is to destroy it.

As I type this, I realize that I could send this blog post and its photos to the UF researchers. This Innovation Park site has a large number of nests, and an association between bees that has only recently been observed and reported. Knowing of a second occurrence of this relationship might be helpful, as might the raw visual data I’ve collected.

I think of how many people must pass this congregation. When it was at its most active, did anyone else notice it? Did anyone stop and watch? I hear a lot of my plant friends use the term “plant blindness” to refer to people who don’t notice the plants around them. A similar insect blindness exists, but it competes with insect revulsion. How many people notice insects, without fear or disgust, and observe them? If more of us did, we might feast our eyes on something new or significant to science. At the very least, we’d find ourselves a little more connected to the natural world around us.