Friday 5 (on Saturday): A Web of Spiders

One of the great things about working at a field station run by a natural history museum is that you’re surrounded by people who share your interests.  This is no small thing when you’re an entomologist!  Sure, we get along famously with other entomologists, but once we leave the comfort of our own kind, we’re exposed to a lot of squeamishness and people who really don’t get  how we could possibly be interested in insects for any purpose other than figuring out how to kill them as quickly as possible.  It’s GREAT to be around other people who appreciate nature when you love nature, and it’s part of the reason why I love my job.

Case in point: yesterday morning, a museum retiree stopped by our lovely construction trailer/office to chat for a few minutes.  He’s a great guy and incredibly knowledgeable, so we discussed a few of the trees in the arboretum he’s built in the lowland area of the field station over the last few years and a few other things before he headed out.  He wasn’t gone long though!  He came back in about 20 seconds later saying, “You all have GOT to come see this!!” and rushed back out the door.  I was thinking he’d seen the sort of thing that most people at Prairie Ridge get excited about, a large bird, snake, or mammal, but instead he’d found a stick mantid egg case on the underside of the handrail for the stairs to the other entrance to the trailer.  Woo!  Stick mantids are cool, so I was excited.  We had admired the egg case for a few moments when the arborist looked up and pointed at this with a big grin on his face:

scarab in spider web

Scarab in spider web

A scarab beetle was dangling from a large spider web!  Clearly it had gotten tangled in the web and had been trapped.  But neither the web nor the beetle were what excited our arborist.  It was this little dew drop spider:

Dew Drop spider

Dew drop spider

That spider was about 1/4 inch long and was EATING THE BEETLE!  The arborist was practically bouncing up and down as he watched the little spider eating the beetle.  These spiders are cleptoparasites, animals that steal food that other animals have captured.  In this case, our little spider was feeding on a large beetle that had been trapped in the web of a much larger orb weaver spider.  The orb weaver was hidden inside the handrail or the day, so the little dew drop spider was helping herself to some food.  The arborist started looking at the web, saying that it was likely that a much smaller male was hanging around too.  Sure enough, there he was, a couple of inches away!

male dew drop spider

Male dew drop spider

At this point, we had a complicated food web going, with a small cleptoparasitic dew drop spider stealing food from a larger predatory orb weaver spider that had captured it, all while a male dew drop spider looked on.

That alone would have been pretty cool, but things got more exciting when we startled the little dew drop spider and she dropped onto the stairs below.  She stayed completely still for several minutes as we all watched to see what she would do.  She eventually made her way over to the handrail, her swollen abdomen flopping from side to side.  We were watching her crawl up the handrail support and debating whether she was full of eggs or not when the arborist exclaimed, “Wow!!!  Did you see that??!!”  He pointed at this:

Jumping spider eating dew drop spider

Jumping spider eating dew drop spider

A little jumping spider, likely a juvenile of one of our larger jumper species, had dashed out of the space between two of the handrail supports and snagged the dew drop spider!  So, now we had a predator eating a cleptoparasite who was stealing food from a predator while the male dew drop spider looked on.  Quite the complicated little food web was developed!

We watched for a few minutes as the jumping spider carried the dew drop spider’s limp body before the arborist wandered back to his car and the rest of us headed back inside.  I looked over the photos I’d taken and realized that I hadn’t gotten any decent shots of the male spider, so I went back out to snap a few more shots.  As I walked past the handrail, I looked to see how far the jumping spider had gotten in devouring the dew drop spider.  Right at that moment, another jumping spider entered the mess, attempting to grab the first jumper!  The attacker missed and the jumper with the dew drop spider scurried away.  I followed the second jumper around with my camera for a few minutes, and it eventually crammed itself down into a little gap between the handrail and the support and looked out at me:

jumper in gap

Jumper in gap

If the second jumper had succeeded, it’s hard to say how the food web would have been impacted.  If it had eaten the other jumper, that would have been a predator eating a predator that was eating a cleptoparasite that was stealing food from another predator while the male dew drop spider looked on.  If, however, the second jumper had snatched the dew drop spider away from the first jumper, it would have been a cleptoparasite eating food captured by a predator who had caught a cleptoparasite that was eating food captured by a predator as the male drop spider looked on!  Regardless, there were 5 different players in this little drama, and that was on a single spider web on a single handrail on an ugly construction trailer where my office is located.

This all illustrates a point: nature is complex if you take the time to look.  If you have a few people who are willing to watch a crazy complicated little spider-focused food web develop with you, well… That makes the experience even better!  I consider myself lucky to work with people who will gladly spend 15 minutes watching little spiders on a handrail.  Here’s to many more similar adventures in the future!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth
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16 thoughts on “Friday 5 (on Saturday): A Web of Spiders

  1. well observed (in the first place) and well documented: that whodunit list of ambush predator eating cleptoparasite while … had me thinking at the start of the morning.

    • Glad to hear it! I was thrilled to be able to see the whole saga – and I imagine that even more exciting things would have happened if I’d hung out longer, but I unfortunately had work I couldn’t put off and had to go back inside.

  2. Spider train! This reminds me of the total joy I experienced once, observing a little native bee, when I realized a jumper was watching the same insect from a flower nearby. We were hunting together.

  3. The jumper eating the other spider looks like an immature Phidippus audax. The second salticid is a female Platycryptus undatus.

    • Yeah, we were leaning toward audax for the jumper eating the dew drop spider. How can you tell the lighter colored one is Platycryptus? I am far from great at spider IDs, so I’m interested in learning more about the characters you used for that.

      • I guess just general gestalt. P. undatus are distinctive in eastern North America, and nothing else really looks quite like them. The females are big, mottled gray spiders, with dark gray to blackish lateral stripes on the abdomen, a paler leaf-like marking down the dorsum, and with a white clypeus. The males are much more gracile, and have an orange clypeus. They are pretty common on tree bark and old, weathered buildings and fences.

  4. I can’t match the food chain story, but I did once observe a fascinating spider behaviour. I saw a small caterpillar, wrapped in spider silk, being hauled up to the inside of an air conditioner lid (the corner where all the pipes enter the unit). There were two silk strands, connected to each end of the unfortunate caterpillar, and converging on a point inside the top of the unit where a hidden spider was doing the hauling, first on one thread and then, when that thread was taking all the weight, switching to pulling on the other. I thought that was really clever – that it would only be pulling up half the weight of the caterpillar at any given time.

  5. Pingback: Expiscor (5 August 2013) | Arthropod Ecology

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