Photo of the Week – July 20, 2017

Wow, this was a hot week.  About the time I stopped hiking hills and collecting data at the Niobrara Valley Preserve yesterday, my truck’s thermometer said it was 111 degrees Fahrenheit.  Sure, it was really hot, but I figured the truck was probably estimating a little high until Kim said she looked at the official weather report from Valentine (nearby town) and it said the high recorded temperature there was 112 degrees.  That’s pretty hot for northern Nebraska.

One of the reasons I was trudging through the hills in the heat was to look for lizards, but I’m pretty sure they were smarter than I was and were hanging out in cool shady places, because I didn’t see any after about 11 am.  The insects in the prairie seemed less affected by the heat, however, and I saw lots of them, including quite a few gorgeous red assassin bugs.

These assassin bugs didn’t seem to be affected by the extreme heat. I spotted them near where I parked my truck on a hill and they were still there over an hour later when I finished walking my transects.

Wasps also seemed to be particularly abundant this week, especially on the blossoms of sand milkweed and other wildflowers.  I enjoyed looking at the diversity of wasp species, but my enthusiasm diminished very suddenly when one of them (I’m pretty sure) stung me in the back.  I think it must have gotten itself wedged between my pack and my back.  It wasn’t MY fault it got stuck there, but I now have a large ugly welt anyway.  Man, that hurt!  A lot.

The day before I got stung, I spotted a wasp (probably not the same one) in a patch of bare sand, and thought about photographing it.  I glanced down at my bag just long enough to extract my camera, but when I looked back the wasp had moved a few feet and was now grappling with one of those red assassin bugs.

Just because the wasp is on top of the assassin bug doesn’t mean it was getting the upper hand, as you’ll soon see.

Actually, grappling is probably a misleading term because it looked like a pretty one-sided battle.  After a half minute or so, the assassin bug flipped the wasp over and it was clear who was winning.

Getting stung by a wasp on a super hot day wasn’t fun, but this wasp was having a worse day than I was having.  You can see the assassin bug’s proboscis inserted into the abdomen of the wasp, and the bug’s toxin is apparently pretty fast-acting because the wasp was done twitching by this point.

I photographed the scene quickly and then got up to leave.  I must have moved too suddenly for the assassin bug’s liking, though, because it took off and flew a few yards away, leaving the wasp behind.  Even after I kept moving away and left the area alone for a few minutes, the assassin bug didn’t return, so I came back and took one final photo of the dead wasp.  I’m hoping maybe the bug returned to finish its meal later.  I feel bad…

The dead wasp.

I think the wasp pictured above is a male, though I’m not confident of that.  I don’t see a stinger, anyway.  While I was driving home yesterday (with the air conditioner blasting pleasantly), I wondered to myself whether or not assassin bugs can tell male wasps from female wasps.  Apparently wasps can tell the difference, so it doesn’t seem completely crazy that other insects could as well.  It would sure be handy to know whether you’re about to attack a stinger-wielding female or an unarmed male…

Everyone thinks about this kind of thing while they drive, right?

This wasp hung out on a yucca pod just long enough for me to photograph it.

I’m definitely a generalist, rather than a specialist, when it comes to ecology and natural history.  I know a little bit about a lot of species rather than a lot about a selected group.  If I had to narrow myself down, though, wasps would be a group of organisms I’d like to study.  I mean look how cool the blue one above is!  Or maybe I could study assassin bugs.  They’re pretty amazing too.  Or moths…  Or grasshoppers…  Or flea beetles?

Maybe I’d better stick to being a generalist.

Insects After a Hard Freeze

In last week’s Photo of the Week post, I mentioned that I’d spent part of a morning photographing white fluffy seeds in autumn prairie.  (It’s not a bad life, all things considered.)  As I walked that morning, I noticed how quiet it was.  In fact, the only sounds I heard were those of my feet crunching through the dried grass.  We’ve had three below-freezing nights in the last week or so (25, 27, and 28 degrees F), and those cold temperatures have eliminated most insects – and their sounds – from the prairie.

Milkweed seeds in autumn prairie.

However, the prairie was not completely devoid of insects.  As I was photographing seed heads of false boneset (Brickellia eupatorioides), I noticed that one of the flower stems seemed much thicker than it should have been.  Upon closer inspection, it turned out to be a caterpillar.  Anyone know what kind it is?  I certainly don’t.

A caterpillar on a false boneset seed head.

In fact, there were two caterpillars on the same plant.  Did they survive the cold temperatures right there on the plant?  Or did they drop down into the thick leaf litter below during those frigid nights and find enough warmth to avoid freezing?  Are they larvae of a moth that overwinters as a caterpillar?  Or are they the last reproductive gasp of a moth species that migrates north each year in the spring, produces multiple generations, and then finally succumbs to the winter cold?

A second caterpillar on the same plant.

The coloration of the caterpillars matches fall prairie foliage very well, which makes me wonder whether they are of a species that overwinters as a caterpillar – and has protective coloration to match late fall dormant stems.  Maybe one of you will know some of the answers to my questions and can solve the mystery.  That’d be great, but in the meantime, it’s just as much fun to speculate as to know!

The caterpillars weren’t the only insects in the prairie.  Just a few steps away, I found the insect pictured below.  Can you identify it from the front?

Do you recognize the face of this insect?

The photo below gives you a better look.

An assassin bug sits in ambush on the seed head of a dotted gayfeather plant.

The assassin bug appeared to be waiting quietly for another insect to venture near enough to become a meal.  Based on the scarcity of insects in the post-hard-freeze-prairie, that could be a long wait.  Besides the assassin bug and the two caterpillars, the only other insect I saw was a ladybug, though I’m sure there were others that survived the first cold snaps – including wolf spiders.  Long-time blog readers might remember a post from a couple years ago about a wolf spider I found running around on the ice on an 18 degree F day.

So how do insects do it?  They’re cold-blooded, right?  They should be particularly vulnerable to really cold weather…

Well, a good hard freeze does bring death to lots of insects.  However, their species show up again the next year, so they clearly have strategies for getting through the winter.  Many species overwinter as eggs, but others survive as larvae or even adults.  Most of those that overwinter as larvae or adults seek shelter from the worst of the cold by burrowing underground or beneath deep leaf litter.  Even so, they may have to withstand temperatures well below freezing.  Some insects produce a kind of anti-freeze solution to protect themselves from freezing, while others change the way they store liquids within and between their cells so their cells don’t rupture when those liquids freeze and expand.

…and of course there are lots of other strategies.  You can read a technical description of some of those in this research article, if you’re interested.  Or you could read a more general post I wrote last year about winter survival strategies of a number of animals.

What’s happening to the insects in prairies near you?  Have you already seen the big first freeze die off?  Maybe you live in a climate where that never happens?  I’d love to hear your stories.