Thawing Frozen Bugs; The Grand Experiment

A few weeks ago, I wrote a post about seeing insects frozen in ice, and speculated about how they’d gotten there and whether or not they might still be alive.  Several of you encouraged me to chip them out of the ice and thaw them out, apparently under the impression that I walk around with an ice axe in my camera bag.  Nevertheless, it was a fair point.  Why speculate aimlessly about something that’s relatively easy to test – especially since it wasn’t the first time I had speculated on the same topic?  (See this post from 2014 and this one from 2011.)  For my 2014 post, I actually did pull a beetle out of the ice and watched it thaw.  It was dead.

Yesterday afternoon, I went out to our family prairie with two of our boys.  Daniel needed to do some video work for a school project, and Calvin wanted to continue working on a project he’d started over the weekend, which seems to involve propping sticks against a tree.  Anyway, two boys wanted to go to the prairie – what am I going to do, say no?  We went.

The boys had a great time playing on the ice while I was looking at dead bugs.  I should maybe reevaluate my life choices.

It was about 60 degrees when we got to the prairie, and while the wetland was still frozen enough to walk on, the top of the ice was melting.  Scattered about the wetland and a nearby livestock watering tank were numerous insects that had been frozen yesterday but today were sitting in shallow puddles of water on top of the ice.  Ah ha!  No ice axe required today!  I grabbed a ziplock bag from my pack (an item even more essential to a naturalist than an ice axe) and starting scooping up cold insects and enough water to keep them in.

A cell phone photo of a couple insects on the frozen surface of a livestock watering tank.

When we got home, I dumped the bag of pond water and insects into a shallow bowl.  The following is a series of observations as I conducted this important scientific research project.

A bowl of bugs on my kitchen counter.

February 26, 2018

6:05 pm – Dumped 18 insects into a bowl, having collected them from thawing water on top of the ice at our prairie.  (No ice axe required, thank you.)  Initial observation: the insects appear to be motionless.  Some are floating, others are submerged.  Water is still very cold.

6:31 pm – Added a little warm water to the bowl.  Some of the insects moved as I dumped the water in, but seemed to settle back into stillness as the water calmed.  Brief movement considered inconclusive as to the status of insects as living or dead.  More data needed.

7:48 pm – Water is about room temperature now.  Wondering if the floating are the same that were floating earlier?  Probably.  A couple stray legs seem to be lying around on the bottom of the bowl.  If those insects are soon to be alive and kicking, it appears they’ll have fewer legs to kick than they had last fall.

A stray leg.

8:33 pm – Of the 18 insects I collected and put in the bowl, 18 still appear to be motionless.  Fighting boredom (me, not the insects).  Must remain vigilant in order to complete this project for my readers.

9:07 pm – Nothing to report.

10:15 pm – I’m pretty sure several of these insects are actually flies, and not aquatic insects at all.  Wondering if I should remove those from the dataset so as not to bias the overall survival rate.

Waiter, there’s a fly in my soup.  Oh? What’s it doing?  Nothing.  (Not a funny joke at all.)

10:56 pm – So tired.  Can’t keep my eyes open much longer.  Have decided to call it a night and hope not to lose any insects that reanimate during the night and fly off.  Will cover the bowl to be sure. One of the water boatmen has a certain look in its eye – just waiting for me to go to sleep so it can make its escape?  Better seal the bowl tightly…

February 27, 2018

6:15 am – Woke up and immediately remembered the insects.  Hoped none had eaten each other or escaped.  Scurried out to the kitchen and did a quick count.  All 18 insects accounted for.  None seem to be moving.  Sleeping after a busy night of swimming?  Swished the water around a little, and got some movement, but didn’t seem to be the result of any self-propelling motion by the insects.  Hopes diminishing.

7:10 am – Have decided that maybe the water temperature needs to be higher in order to break diapause.  Added hot water to the bowl.  Awaiting developments.

7:15 am – Trying to fix breakfast and school lunches.  Need counter space.  Re-evaluating this entire project.

7:23 am – Adapted Monty Python sketch running through my head…  “These bugs are no more!  They’ve ceased to be!  They’ve expired and gone to meet their maker!  They’re stiffs!  Bereft of life, they rest in peace!…These are EX-BUGS!”

Figure 1. Number of dead bugs compared to number of live bugs.  Error bars represent 95% confidence intervals.

7:24 am – Ok, I’m calling it.  Experiment over.  These insects are dead, folks.  Of the 18 frozen insects removed from the surface of the ice, 18 died.  This evidence strongly supports the suggestion that insects found embedded near the surface of frozen wetlands are, in fact, dead.  This follows the findings of Helzer (2014) who similarly found a frozen beetle to be dead upon thawing.

Pining for the fjords?  Nope.


Ok.  I’m going to clean out that ziplock bag now and get it back in my camera bag.  I don’t want to be left without it when the next scientific opportunity presents itself.

Surviving the Winter

This has been a difficult weather week for many people across the eastern half of North America.  Strong winter storms have dropped tremendous amounts of ice and snow, and extremely cold temperatures and strong winds have made it difficult and unsafe for people to be out and around.  We were on the western edge of this storm here at home, so just had strong winds and a little snow (though still enough to cancel school for two days).  While I was sitting inside my warm insulated house, watching the wind blow the snow around town, it was hard not to think about all the creatures who have survived weather like this for thousands of years – without any of the comforts we see as basic necessities.

Species that don’t migrate to warmer climates have a couple of choices for survival when temperatures drop.  First, they can either hibernate or enter some other form of dormancy for the majority of the winter.  Second, they can stay active and survive as best they can – usually losing much of the fat reserves they build up in the fall.  Third, they can hide away during bad weather and search for food when temperatures are more moderate.  Late last year, I wrote an article for NEBRASKAland magazine summarizing some of the specific winter survival strategies used by Nebraska animals.  If you’re interested in learning more, you can read the full article here.  Otherwise, here are a few short anectdotes you might find interesting…

Water boatman encased in ice in a prairie wetland.

Water boatman

Insects overwinter in a variety of life stages, including eggs, larvae, and adults.  Most enter some level of diapause (a rough equivalent of hibernation for insects) in order to survive.  Those insects that overwinter as adults typically try to find some shelter by burrowing underground or at least into leaf litter or other insulating matter.  Even there, many of them end up freezing solid, only to thaw out and resume life in the spring.  I found this water boatman near the frozen surface of a shallow prairie wetland.  According to several sources I’ve found, these and many other aquatic insects can remain at least somewhat active in the water beneath the ice for much of the winter, but if frozen, can simply thaw out and start swimming around again in the spring.

A surprisingly active leopard frog in a cold prairie stream. The Nature Conservancy's Platte River Prairies.

Leopard frog

Leopard frogs, according to the research I did for the magazine article, are supposed to hibernate on the bottom of ponds where the temperature stays above freezing.  They settle into the sediment at the bottom of a pond, but leave space around the sides of their body where their skin can extract oxygen from the water in sufficient quantities to survive the long winter.  Imagine my surprise, then, when I saw this leopard frog SWIMMING across the bottom of a shallow creek the other day in sub-freezing conditions.  Now, it wasn’t swimming very fast, but it was certainly swimming – not just drifting with the current.  I imagine the groundwater-fed stream was warm enough that it provided the same above-freezing temperatures frogs get from pond bottoms.  In fact, a stream probably has higher oxygen levels.  But still – there was ice along the edges of the stream, and when I saw it stop swimming, I was able to catch up with it and photograph it sitting underneath some of that ice.  It’s not a great image from a photographic standpoint, but tells a story.  I’m not really sure why it was swimming when I saw it (Was it disturbed by me walking by?  Did it get hit by something floating downstream? Does it have to move periodically to avoid getting buried by sediment?) but it gave me something intriguing to wonder about on a cold winter walk.

An oppossum poking around in the snow. The Nature Conservancy's Platte River Prairies.


The opossum is one of a large number of animals (especially mammals and birds) that fit into the “hybrid” strategy category.  During very cold stretches of weather, it stays hidden away in a burrow and has a lower-than-normal heart and breathing rate to conserve energy.  When temperatures warm to a certain point, however, it ventures out to forage and recharge its stores of energy.  This one was poking around in the snow by some tree piles we’d burned the day before, apparently looking for food – but probably also enjoying the little bit of heat still emanating from the remaining embers.  Judging from its uninsulated pink toes and nose, it sure doesn’t look like much of a snow creature (and they do often have ragged frostbitten ears by the end of a hard winter) but oppossums have been around long enough that it’s hard to argue with their success.

Black-capped chickadee in winter.

Black-capped chickadee

Ok, so a chickadee is not exactly a prairie species, but it is a good example of an animal that is known to use a strategy called “daily torpor”.  Chickadees can drop their body temperature a few degrees overnight to save precious calories from being burned during a period when they’re not planning to move around anyway.  Many other birds and small mammals are thought to employ the same strategy, but there’s not much data (that I could find) on the topic at this point.  It certainly makes a good deal of sense, although you’d want to be sure you were in a nice secure place before you dropped into any kind of torpor while owls and foxes were patrolling nearby.


Regardless of your personal strategy for getting through the winter, I hope you’re enjoying this one so far.  Groundhog day has passed, so depending upon your local “hognosticator” you may or may not have a lot more winter to look forward to.

I think I’ll enjoy myself a little daily torpor.