Well-Nigh Wordless Wednesday: The Last Thing Many Aquatic Insects Ever See

If you’re a small, aquatic insect, fish, or tadpole, this image should make you fear for your life:

Dragonfly nymph

Dragonfly nymphs are pretty ferocious, so I imagine that something like this is the last thing many small aquatics ever see, right before that mouthpart snaps out, grabs them, and eats them…

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

Studying Invertebrate Behavior on YouTube

image from class

An experimental setup in my recent insect behavior class. The students were studying how water temperature impacted respiratory rate in the giant water bug Abedus herberti.

As a lab instructor for an insect behavior class, I use a lot of live insects in my class.  The students enjoy working with them and are generally happy they don’t have to watch videos the entire semester.  Trust me – watching hours and hours and hours of insect behavior video can get really dull really fast.  Live insects are definitely the way to go for a class where most of the students do not have the level of patience that I do.

Unfortunately, the class is held in the spring, so there’s just not many insects out until the end of the semester.  This means that my students work mostly with my favorite insects, the aquatic insects, which is good.  However, it also means that they have a fairly limited variety of things to work with, i.e. things that overwinter as nymphs or adults.  I am able to collect a decent variety of aquatic insects during the winter in Arizona.  Still, there is one lab that would be SO much better if we had a bigger variety of insects to work with: the predator lab.

I developed the predator lab four years ago when my students at the time were constantly begging to put two hungry predators together and watch what happened in the ensuing death match.  (Did I mention that my students are college seniors and grad students and NOT 5 year olds?)  In the interest of turning this morbid curiosity into a teachable experience, the predator lab was born.  In it, I have the students feed several different predators and compare and contrast their feeding behaviors.  They have to watch how the insects capture and devour their prey and describe how they do it in detail.  They also have to tell me whether the insect is a sit and wait predator (they stay in one place and wait for food to swim, walk, or fly by), an active predator (they purposefully hunt down and attack their prey), or something else.  This way, the students get to watch several predators capture prey and eat it, fulfilling their need to promote death and destruction, but they are doing it in some meaningful context.

The predator lab is my favorite.  It requires a lot of work on my part to collect the insects and prepare the containers and prey items for the bugs, but the students get so into the activity that I can’t help but love it.  Even my quietest class, the class I just finished last month, got into it and actually made some noise in class for once!  And things get even better toward the end of the class period when they have finished their work for the day and I let them feed the things that don’t survive well in the lab to my water bugs or to each other.  This is the treat at the end of the semester, their reward for making it through what I consider a very work-intensive course: the death match they’ve been eagerly hoping to set up all semester.  This year there was also a water bug eating a fish to watch (click on the link to see the video!).  That really got the students excited.

Unfortunately, this year was a terrible year for aquatic insects in my part of Arizona.  We got a ton of rain during the winter and there was extensive flooding in the mountain streams that washed out the insects.  The populations didn’t rebound very quickly and there was hardly anything in the streams even several months after the floods.  I was hard pressed to get enough insects for my class this year and we ended up with a measly three types of insects for the predator lab this year: some small predaceous diving beetles, some dragonfly nymphs, and some of the smaller giant water bugs.  It doesn’t take very long to feed a hungry insect, so I brainstormed ideas for activities to fill up half of the class period.  I eventually settled on something I knew the students would love: showing some of the spectacular videos of predatory insects on YouTube.

YouTube is a rather amazing repository of insect behavior data.  A lot of the video is collected by amateurs and many of them know very little about the insects they’ve filmed.  That doesn’t matter – there is some great stuff on there if you know where to look!  For my class, I chose some of the most showy videos I could find.  My students had spent the semester watching live insects.  A video has to be amazing to hold my students’ interest at the end of the semester and the 8 videos I settled on fit the bill well.  And because they are too good not to share, I am posting them here so that everyone who reads my blog can see them too!

Army ants:

Damselfly eating another damselfly – check out the mouthparts moving!:

Preying mantis vs. mouse – and the mantid wins!:

Centipede vs. mouse – and the centipede wins!:

Spider captures and kills a bat:

Antlions (are awesome!):

Orchid mantid captures fly:

I can safely say that this was an excellent way to kill some time in class.  The students loved the videos (there were several collective cries of “Whoa!” during lab that day!) and actually learned something in the process.  A few of them even referenced the videos in their lab write-ups!  It was so successful that I think I will do this again the next time I have an opportunity to teach a behavior class, even if I do have a lot of animals to use in class.  It was great for the students to get to see some things we couldn’t possibly duplicate in class and let them see some more insects in action after their regular lab activities.  It was a great way to finish the last lab of the semester.

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com.

A strange fall visitor

While I hear stories of blizzards and frigid weather in other parts of the country, here in southern Arizona it’s still quite warm.  Unseasonably warm actually.  I had to wear a jacket for a few days a couple of weeks ago, but then it got hot (as in almost 100 degrees!) again.  Luckily for me, this means that there are still a lot of bugs out.  A few days ago, my coworker and I tried to catch some painted lady butterflies when we got back to the office after our field work.  The bird of paradise plants and the other things planted with them are still in bloom, so there are still tons of painted ladies and sulphur butterflies flitting around.  Yesterday, I was on my way out to run errands when I saw this on the wall of my carport:

Mantid

Mantid

As I always do when I find mantids outside, I ran back into the house and grabbed my camera, snapping some quick pictures of it before I did my errands.  It was still in the carport when I returned, so I scooped him up and brought him in the house to take some better photos indoors where the light was better.  The image above is one of those.

I love mantids.  I think they are amazing and beautiful animals.  Unfortunately, I don’t see them all that often.  It’s hard to find them most of the time.  They are masters of camouflage, or blending in with their environment, so I just don’t notice them.  Mantids are known to mimic all kinds of plants and flowers (to see some amazing mantid flower mimics, see this great blog post from Asia), tree bark, sticks, and other insects, so they are very hard to see if you’re not actively looking for them.  But that’s the point!  If you want to avoid being eaten, one great way to do it is to blend in with the background so effectively the predator doesn’t even notice you’re there.  If you’re an ambush predator (more about this in a moment), it also helps if the things you want to eat can’t see you very well.  I put the mantid pictured above into the bush in front of my house when I was finished photographing it.  It wasn’t the kind of plant this mantid would normally be found in, but it was still a little hard to see:

camo mantid

Mantid camouflage - can you find it?

This particular mantid was bright green against the deep rust color of my carport when I found it, so it really stood out.  It didn’t take much skill to find this one before I put it in the bush!  I have an idea of why this might be, but I’ll get to that later.

Mantids have some very interesting behaviors.  Their amazing abilities to mimic the plants they live on don’t end at their coloration and body shape.  They are also well-known for mimicking leaves and plants blowing in the breeze.  They use their hind and middle pairs of legs to sway back and forth gently every now and again.  If they are living on plants and want to blend in, it’s to their benefit to mimic the plant as much as possible.  This includes moving the way the plant does – the swaying behavior helps them look more like the plant than their coloration and body shape alone.  Whether they use this behavior specifically to avoid detection is debatable, but it helps them blend into their environment regardless of its primary purpose.  The mantid I found yesterday started swaying when I went to grab it in what may have been a rather desperate attempt to avoid detection and capture, so I got to see this behavior in action.  If you’d like to see it too, check out this YouTube video (which I did not take):

Isn’t that fun?  Just picture this mantid swaying on a stick being gently blown in the wind.  I love watching these little mantid “dances!”

Many mantids are ambush predators, which means that they sit and wait for food to come near before darting out to capture their prey.  Because they blend in with their environment so well, many prey animals won’t notice a mantid sitting on a plant or on a flower and walk right by it.  The mantid then uses it’s forelegs to reach out and grab the prey with amazing speed.  Like the giant water bugs I study and have written about in earlier posts, mantids have what are called raptorial forelegs.   These are legs that are specifically designed for capturing prey.  They’re big and bulky and full of muscles, so they’re both very fast and very strong.  They can often fold back on themselves to allow them to grasp things.  People have long thought that mantids have the appearance of praying when they hold their legs ready to grab prey, hence the common name praying mantis.  Mantids also frequently have spikes or other structures that help them keep hold of things they grab.  Check out the raptorial forelegs on the mantid from yesterday:

Mantid raptorial foreleg

Mantid raptorial foreleg

This one has bulky forearms and some pretty formidable spikes!  Those spikes help them subdue prey so they can eat them.  And mantids can eat some pretty impressive things including other insects, small snakes, lizards, frogs, small rodents, and even the occasional bird!  If they can grab it and keep a hold of it, they’ll likely try to eat it.  I think this is part of why I like mantids so much – they remind me of my water bugs in their ability to capture, subdue, and consume their prey, and they just look so darned cool doing it!

So back to why I think this bug was in a strange and very conspicuous spot.  If you have a weak stomach, this is where you should stop reading.  I went out to the bush where I had released the mantid this morning to see if it was still there and was sad to see that it had died overnight.  Because I’m an entomologist, my first thought was, “Wow!  It’s sad the mantid died, but it would make a great addition to my collection!”  So, I brought it inside and started pinning it.  Much to my horror, as soon as my pin hit the abdomen, I disturbed the mass of maggots that were growing inside the mantid and feasting on its living flesh.  They burst out of the mantid and spewed onto my counter.  Now I’m not a very squeamish person, but maggots spewing out of anything is enough to make me queasy.  I ended up preserving the maggots in alcohol (why collect one type of insect when you can add two to your collection?) and will figure out what they are later, though I know they are a type of parasitic fly.  An adult fly likely deposited its eggs inside the mantid a month or two ago and the maggots slowly consumed the living mantid as they developed.  Parasites are known to alter the behavior of many insects they infest so that they are better able to infest other organisms.  It’s quite possible that the maggots altered the behavior of this mantid when it was near death so that it made itself conspicuous enough to come into contact with another animal that the maggots could use as food.  Alternatively, it could simply have become delirious as its body was hollowed out and mistakenly crawled up a surface it would normally avoid.  Whatever the reason, it didn’t matter that it was in a conspicuous place – it was dying anyway.  And I’m happy I got to see it before it did.  A mantid will always brighten up my day.

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Text and images copyright © 2009 DragonflyWoman.wordpress.com