Web-Watching and Wondering

As often happens, watching something closely doesn’t necessarily help me understand what I’m seeing. Fortunately, a lack of clarity doesn’t detract from my enjoyment of the observation! I have guesses about what was going on with the two banded garden spiders I hung out with Sunday morning, but I’ll be curious to know if any of you have additional thoughts.

Last weekend, Kim and I traveled down to Konza Prairie Biological Station, a deservedly-famous site for both prairie and research in the Kansas Flint Hills. Kim’s reason for the trip was that she wanted a site with some hills and scenery for a long training run. I was more than happy to tag along. We arrived before sunrise and both took off up the public hiking trail – at very different speeds and for very different reasons.

It wasn’t an ideal morning for photography, but was still a great day and place to enjoy a prairie hike. The strong breeze was nice for Kim, but frustrating for me, and once the sun cleared the horizon, its light became overly intense pretty quickly. After an hour or so of pleasant hiking, but limited photography options, I retreated back down to the trailhead.

There, I took advantage of some trees that were blocking some of the wind and providing a little diffused light. I looked around for insects to photograph and laughed at myself for being grateful for having trees in a prairie. That doesn’t happen very often.

The trees near the trailhead blocked some of the wind and also created some diffused light along the edge between sun and shade. I worked that edge, looking for photo subjects.

I did find some interesting insects to photograph, but also spotted several big banded garden spiders (Argiope trifasciata). Since the trees were blocking some of the breeze, I decided to try photographing them on their gently-undulating webs. As I tried to decide where to start, I noticed a smaller male spider hanging out at the top of a big female’s web. It was far enough away that I had to back off and use a long telephoto lens to get both spiders in the same shot.

A female banded garden spider
The male (top) and female (bottom) banded garden spiders.

When a male shows up on a female’s web, it’s usually because it’s mating time. This is a very tricky situation for males, who often get caught and eaten as soon as copulation is completed. You might say the trick for the male is to get mating wrapped up without getting himself wrapped up.

Here’s a closer look at the male.

As I watched, the male carefully made his way down the web toward the female. Based on prior reading, I knew there were signals he could give to alert the female that he wasn’t prey (yet) but I couldn’t pick up on anything specific he was doing. He stopped a few inches from the female and waited. That was when I noticed his missing legs. I wondered if he’d escaped a previous mating situation, but lost his legs in the attempt (this is apparently common).

The male and female closer together (and easier to photograph!)

After several minutes of sitting still, the male started moving again. This time, it looked like he was intentionally ‘plucking’ the web to alert the female to his presence again before crawling down to her. He quickly scrambled around her body until he was in position to deposit sperm from his pedipalps (the little appendages by his mouth) into her epigynum (the place sperm goes into a female spider).

The male making his way quickly into position.
He’s in position. The epigynum is right below his head.

Once he was in position, I figured the drama would ramp up as the female tried to grab him and hold him there until he did his job. She didn’t. Also, he only stayed in position very briefly (a second or so) before quickly skedaddling up onto the web again. He stopped a couple inches away and sat for a while.

Here’s a different angle on the two spiders, showing their top (dorsal) sides.

Hmm…

Did he lose his nerve? Did something go wrong? I waited a few more minutes, and sure enough, he tried again. The same process occurred – he plucked the web, ran down onto her, got into position, and then quickly climbed back up again. She was making some movements with her legs in response to him approaching, but I didn’t know how to interpret those.

I ended up spending the better part of an hour watching the spiders. During that time, the male approached and left the female at least half a dozen times. From a photography standpoint, that was great because it gave me multiple chances to capture the action. It seemed odd, though.

When I got home, I looked closely at the photos I’d taken and did some online research. I have a hypothesis now. See what you think.

I read more about the risks of mating, from the male’s standpoint. Many of them are killed during the first attempt, but some (20%, according to one source) escape and try to find a second female to mate with. Usually, that second mating is their last, and there was some suggestion that the male will voluntarily succumb to the female after that second occasion.

One reason mating might be limited to two tries is that some male spiders actually break off a pedipalp inside the female’s genitalia – presumably as a way to block sperm from other males who might stop by after he leaves (or dies). Spiders only have two pedipalps, so after two mating attempts using that strategy, I guess there’s no point in continuing. Maybe that’s why the male often gives himself up to that second female. If nothing else, he’s ensuring she gets a good meal and is in better condition to raise his kids.

After reading all that, I went back to my photos and saw something that triggered my hypothesis. Look at this last photo of the male. Those pedipalps don’t look right to me. Male spiders should have bigger pedipalps than that.

The small (and withered?) tips of these pedipalps make me wonder if they’d been broken off.

Did this male already mate twice, losing a couple legs during his escape(s) and leaving the tips of both pedipalps behind? If so, instead of giving up, he apparently decided to live on, and maybe was driven by instinct to keep trying to mate (without the appropriate equipment to do so). That might explain his quick visits and retreats from the female.

If that’s true, I feel really bad for him. He worked up the nerve to approach a very dangerous female spider (maybe for the third time!), but when he arrived, he couldn’t actually do anything. That had to be confusing, and likely frustrating, depending upon how spiders experience emotions in situations like this. The poor little guy then just kept trying, each time hoping he’d have better luck.

Here’s a closer look at those pedipalps.

Another possibility is that the male spider was born with deformed pedipalps. That would create an equally-sad scenario. Well, maybe even more sad because in the first scenario, at least the male got to mate a couple times. In the second, he didn’t even get that opportunity.

Long after the day got way too hot for my comfort, Kim finished her 25 mile run. Once she cooled off, I took her over to see the two spiders. They were still sitting two inches apart, which I figured meant the male was still making periodic (and fruitless?) approaches. They’d been there for more than three hours at that point.

I wonder how the story ended. Did the female eventually give up and just eat the poor guy? Did he eventually give up and wander off? Either way, it’s not a real heartwarming story, huh?

If one of my two hypotheses is right, I’m hoping it’s the first one – that he mated twice and then didn’t know when to stop. At least in that case, he’s got a decent chance of passing his genes onto a future generation.

Anyone have a better explanation for what I saw?

Photos of the Week – September 29, 2023

Early this week, I spent about 24 hours at the Niobrara Valley Preserve, helping with an event for members of The Nature Conservancy. In between (and sometimes during) tours and conversations, I managed to get a few autumn photos of the prairie and river valley.

When I woke up Tuesday morning and saw fog outside my window, I knew my plan to sleep in wasn’t going to happen. I drove up the hill and started wandering. The fog was mostly settled down in the river valley, so I looked for opportunities to photograph it with the pre-sunrise color in the background.

Morning fog in the Niobrara River Valley at sunrise. Tamron 100-400mm lens @210mm.  f/5.6, 1/100 sec.
Fog and fence at the Niobrara Valley Preserve. Tamron 100-400mm lens @100mm.  f/5, 1/125 sec.
More of the same, different angle. Tamron 100-400mm lens @100mm.  f/8, 1/60 sec.
Layers of hills and trees with river fog, clouds and sunrise. Tamron 100-400mm lens @400mm.  f/6.3, 1/640 sec.

As the sun rose through the fog and scattered clouds, I tried several times to photograph it behind various plants. That mostly failed, but I did find one composition I liked with some sand bluestem flowers silhouetted in front.

Rising sun behind sand bluestem (Andropogon hallii). Tamron 100-400mm lens @400mm.  f/6.3, 1/2500 sec.

Smooth sumac is a native shrub that is both a blessing and curse at the Niobrara Valley Preserve. It’s a gorgeous plant, especially in the fall, and provides lots of resources for lots of animals. There’s also an AWFUL lot of it.

Based on aerial photos, we’ve got lots of patches of sumac that are hundreds of acres in size. On the north side of the river, the 2012 summer wildfire that swept through the area killed most of the ponderosa pine and eastern red cedar trees on the hills and ridges. The footprints of those dead trees quickly filled with sumac and the shrubs have spread from there. We’re experimenting with ways to suppress and shrink sumac patches, but it’s challenging in steep topography, and at the scale we’re dealing with.

Still, sumac is sure pretty when it turns red…

Backlit smooth sumac. Nikon 105mm macro lens.  ISO 400, f/14, 1/60 sec.
Grasshopper on smooth sumac. Nikon 105mm macro lens.  ISO 640, f/18, 1/80 sec.
Nikon 105mm macro lens.  ISO 640, f/14, 1/250 sec.
Smooth sumac leaves. Nikon 105mm macro lens.  ISO 640, f/14, 1/250 sec.

While the fog stayed down in the valley, it was still plenty dewy up in the Sandhills where I was walking. That meant opportunities to photograph insects covered in water droplets, though their numbers were considerably lower than they were during my last visit. I found a bejeweled mayfly and lots of grasshoppers, but no dragonflies or butterflies (though I saw a few of each later in the day).

Mayfly and dew on switchgrass (Panicum virgatum). Nikon 105mm macro lens.  ISO 640, f/16, 1/400 sec.
Dewy grasshopper on sand bluestem. Nikon 105mm macro lens.  ISO 400, f/14, 1/60 sec.
Grasshopper perched on plains sunflower seed head (Helianthus petiolaris). Nikon 105mm macro lens.  ISO 640, f/16, 1/400 sec.

Later in the morning, we took our visitors on a birding hike. I wasn’t the primary tour leader, so while everyone else was looking up at birds, I was looking down at tiger beetles, moths, and spiders. I pointed them out to our guests, of course, but also lagged behind the group for a while and tried to photograph them. Some of that included lying prone in the wet grass to get the right angle, which provided a little extra entertainment for the group.

Spider on her dewy web. Nikon 105mm macro lens.  ISO 640, f/13, 1/1600 sec.
The same spider from a different angle. Nikon 105mm macro lens.  ISO 640, f/18, 1/3200 sec.

Aside from the orb webs most people think about when they envision spiders, there were also small tangled webs at the tops of plants – especially switchgrass. I used to assume these were primarily shelters built to protect spiders from predators, etc. As I started looking closer, though, I noticed all the carcasses of small insects caught within the webbing. Clearly, these webs were more effective at catching prey than I’d first assumed.

Spider hiding in its dewy, silken shelter. Nikon 105mm macro lens.  ISO 400, f/13, 1/160 sec.

The tiny spiders in the tangle webs were tough to photograph Tuesday morning because they mostly stayed concealed within their dewy dens. I tried to find angles that showed at least a few legs. I did see a few of them spiders moving around, but most of them slipped back into cover as soon as I got within a few feet. As they should, of course.

I finally managed to get a couple shots of one of the little spiders before it scooted away. These spiders are really small. They were maybe half the diameter of a pea. Or, if you prefer a more modern reference, they’d be able to squeeze into a USB-A port on a laptop or other device.

The same species of spider (I’m pretty sure) in a different web. Nikon 105mm macro lens.  ISO 400, f/18, 1/80 sec.
Examples of the prey caught by these spiders. Nikon 105mm macro lens.  ISO 400, f/18, 1/80 sec.

We had a great trip. The fall weather was splendid and our guests were curious, interested (and interesting) people who really seemed to enjoy everything we showed them. I was more than happy to help find things for them to be enthusiastic about!

Members of The Nature Conservancy enjoying a campfire and stars at the Niobrara Valley Preserve. Nikon 10-20mm lens @10mm. ISO 1250, f/5, 5 secs.