Favorite Little Predators

Those of you who have followed this blog for a while are probably familiar with my minor obsession with crab spiders.  I have an awfully hard time passing up the opportunity to photograph them when I spot them.  Because I spend much of my work time looking at plants, I see a lot of crab spiders, sitting stoically in ambush, waiting for unsuspecting prey.

As it happens, I’ve already found and photographed a few crab spiders this week.  One, in particular, was a lot of fun to watch.  I spent most of Monday collecting plant data (in a walking boot, which is frustratingly slow, but a great deal better than crutches).  Though it was windy, there were periods of nice light, thanks to some passing diffuse clouds.  During one of those periods, I spotted a yellow crab spider crawling up a dead grass stem.  I paused to see what it was going to do, reaching slowly for my camera.  When it got to the top of the stem, it released a long burst of silk into the wind, and soon thereafter starting crawling along that silken thread to another grass stem a few feet away.

A crab spider prepares to pull itself along a long thread of silk it had just released into the breeze.  I got to watch it travel between several tall perches this way over the period of a couple minutes.

By this time, I had my camera out and was crouched low, trying not to spook the spider as I crept toward it.  It worked its way up its new grass stem and repeated the process of spooling out more silk.  This time, I got lucky, catching a brief pause in the wind just as the spider prepared to follow its new travel line to another plant.  I squeezed off several shots with my camera and managed to get at least one that was sharp.  As I watched it make its way along its high wire, the wind kicked back up and the harsh mid-day sun reappeared from behind a thin cloud.  I wished the spider well and went back to counting plants in my plot frame.  I sure like crab spiders…

When I got back to town Monday night, I had a few minutes and figured I’d take a quick trip to my square meter plot to see what was happening there.  A few high clouds were moving toward the sun so I hobbled down the short trail toward my plot, hoping for a few minutes of decent light.  As I was nearing a patch of plum and other shrubs, I saw a bumblebee land on a high branch.  I just about kept walking, but something was odd – it looked like the bumblebee was carrying something in its mouth.  Just as my mind starting to put things together, the bee took off again and landed a little closer to me.  I froze and reached slowly for my camera, having just recognized that the bee wasn’t a bee at all.

If crab spiders are my favorite invertebrate predator to photograph, robber flies are surely my second favorite.  Though tiger beetles are pretty awesome too.  Oh, and assassin bugs!  Also praying mantises…  But I digress.  I really like robber flies, and what I had thought was a bumblebee was actually a robber fly species that mimics bumblebees, and it was carrying a small beetle it had just caught.  I’ve read about these but had never gotten close enough to one in real life to have a chance to photograph it.

I knew the fly wasn’t likely to sit for long so I didn’t bother with a tripod and just hand held the camera as I crept toward my quarry.  Trying to stabilize my camera and cursing the wind, I started shooting like crazy as I got close (thank you digital photography!).  I had about 5 seconds within reasonable range of the fly before it took off and flew out of sight.  Out of the roughly 10,000 photos I took during that 5 seconds (ok, maybe 20), I got exactly one that was sharp.

A bee-mimic robber fly (Laphria sp.) at Lincoln Creek Prairie in Aurora, Nebraska.

I’m an unabashed fan boy when it comes to insects, spiders, and other invertebrates, but can you blame me?  How could anyone not love a predatory fly that looks nearly identical to a bumblebee?  All robber flies are voracious predators that can snag flying insects out of the air and neutralize them with toxic saliva.  The saliva also liquefies the innards of the fly’s prey, allowing it to just suck its dinner out of the convenient container made by the hapless insect’s shell.  Those qualities alone make robber flies plenty endearing – or terrifying, if you’re a tiny insect.  Adding a near-perfect disguise to the mix, allowing them to cozy up to unsuspecting pollen feeding insects is really unfair.  But, wow, it’s cool!

I got one more look at the bumblebee mimic on my hike back out from my photo plot, but it didn’t stick around for photos the second time.  Fair enough.  Just getting the opportunity to spot the fly-that-would-be-a-bee was enough to make my day.  Photographing it was icing on the cake, and also gave me the chance to share the whole experience with you.

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About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.
This entry was posted in Prairie Insects, Prairie Natural History, Prairie Photography. Bookmark the permalink.

7 Responses to Favorite Little Predators

  1. marknupen says:

    reminds me of the fun we had playing cops and robbers, good guys and bad guys, as kids.

    Ah, the stealth and the capture. Yes, indeed, fun to watch! HAH!

    thanks

    On Wed, Jun 13, 2018 at 6:15 AM, The Prairie Ecologist wrote:

    > Chris Helzer posted: “Those of you who have followed this blog for a while > are probably familiar with my minor obsession with crab spiders. I have an > awfully hard time passing up the opportunity to photograph them when I spot > them. Because I spend much of my work time lookin” >

  2. Paul Brewer says:

    One of my favorite recent posts Chris, and glad to see you gimping around well enough to still find amazing things to photograph!! As always, I appreciate what you share with us!

  3. Don Hunter says:

    I’m a big crab spider fan, as well, here in the southeast U.S. Ounce for ounce they are probably the most badass things out there. Re: the robber fly, that is probably the most complete and amazing example of mimicry I have ever seen. What a score!

  4. Patrick says:

    Great photos. Yes, this particular species of robber fly is really fun to watch, because they’re fairly large and boldly colored. They tend to have a favorite perch or two that they use to survey their surroundings, just like a cheetah on a termite mound or a leopard in a tree.

  5. Karen H. says:

    You sure are getting a lot of mileage out of that broken foot :)

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