Friday 5: Five Types of Insect Legs

We entomologists value precision, especially when it comes to the study of the structures of insects, called insect morphology.  There are endless names for highly specific parts that are useful in identifying insects.  However, these can get a little confusing to people who aren’t entomologists.  Consider this example, used in an identification key to differentiate one subfamily of crane fly from another:

Terminal segment of maxillary palpus elongate. nasus usually present, antennae usually with 13 segments, wings with Sc1 usually atrophied

If you have absolutely no idea what that means, you’re not alone!  And it’s not important for now anyway.  Just know that insects are supremely adapted to a wide variety of habitats and they thus exhibit a wide range of structures that allow them to live in so many different places.  For example, different insects have different styles of legs that best fit their lifestyle and the type of habitat they live in.  To give you a little taste of some of the variation you see in insects, today I’m going to cover 5 types of insect legs:

cursorial leg - cockroach

cursorial leg - cockroach

1.  Cursorial legs. These are the types of legs most people likely think of if they’ve ever pondered insect legs before.  Cursorial is a fancy word for running, so these are the kinds of legs you see on swiftly moving insects such as roaches and tiger beetles.    Cursorial legs tend to be long and narrow and are designed so that the insect can move very quickly.  Things with this type of leg are often hard to catch – or hard to step on if you’re dealing with roaches.

saltatorial

saltatorial leg (grasshopper hind leg)

2. Saltatorial legs. Saltatorial legs are jumping legs.  You’ve all seen these kinds of legs before!  Grasshoppers are the poster insects for saltatorial legs, but other jumping insects like fleas have them as well.  Saltatorial legs work well for jumping because they are enlarged legs filled with bulky, strong muscles.  All those muscles allow insects with this type of leg to jump, propelling themselves forward very long distances very quickly.  Saltatorial legs are usually hind legs.

raptorial leg

raptorial leg (giant water bug foreleg)

3. Raptorial legs. You are likely familiar with this sort of leg too.  Raptorial legs are hunting legs, the kinds of legs you see on predatory insects such as mantids and giant water bugs.  Like the saltatorial legs, these are enlarged legs full of strong, powerful muscles.  However, these legs are usually at the front of the insect and are used to grab and hold prey while they eat.  Many insects with raptorial legs hold them out in front of their bodies, positioned so that they can strike at prey at any time.

natatorial leg

natatorial leg (predaceous diving beetle hind leg)

4. Natatorial legs. Natatorial is another word for swimming, so insects with natatorial legs are aquatic insects that require modified legs to move easily through water.  Natatorial legs are often flattened, broad, and fringed with dense hairs, as in the image of the predaceous diving beetle hind leg pictured at right.  These adaptations have the same sort of effect as a human wearing flippers as they swim – they increase the surface area of the legs as they kick, allowing the insect to move more easily through water.  Many aquatic insects exhibit natatorial legs, especially in the hind and middle pairs of legs, but not all of them do.  They are especially common in aquatic beetles and bugs.

fossorial leg

fossorial leg (mole cricket foreleg)

5. Fossorial legs. Insects with fossorial legs live underground and use their highly modified legs, usually the forelegs, to dig burrows.  The mole cricket, the forlegs of which are pictured at left, are a prime example.  Fossorial legs tend to be very broad, very flat, and very dense.  They often have big, strong claws.  Fossorial legs work somewhat like shovels to rip soils apart quickly and easily and allow the insect to bury itself in the ground surprisingly quickly. This type of leg is much less common than the others, but it’s a thrill to find an insect that has them!  They’re really impressive.

So now you know some fancy words to describe different types of insect legs! You never know when this sort of knowledge might come in handy.  At a cocktail party, winning that big jackpot in Final Jeopardy, when naming you new rock band, to impress a girl/boy – the possibilities are endless!

Tune in next week for 5 aquatic insects that suck!

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

Collecting Insects: A Net for Collecting Aquatic Insects

It’s been too long since I last posted a tutorial for my Insect Collections series, so today I’m going to share my best secret for collecting aquatic insects.  A lot of people overlook aquatic insects when they work on their collections.  It’s a shame really – there are some fantastic insects in water if you take a few minutes to look!  I think part of the problem is that most people think you need to have fancy nets that cost $60+ or other special, expensive equipment to collect in water.  This couldn’t be further from the truth!  Today I’m going to show you how to make and use a reasonably sized, easy-to-carry aquatic net for collecting insects in water, one that my advisor recommended to me when I started grad school.  Are you ready for this complicated design?  Breathe in through your nose and out through your mouth to prepare your mind for the complicated steps this tutorial is going to involve.  Ready?  Then gather the things you need:

Essential Equipment

soup strainer

Essential equipment

  • one sturdy all metal kitchen strainer, preferably stainless steel.  (A solid frame around the basket is essential, so make sure that part isn’t going to collapse or separate from the handle if you put a little pressure on it.)

Whew!  Are you tired yet?  And if you want to be REALLY fancy, then you’ll want these things as well:

Optional Equipment

strainer extras

Optional equipment

  • metal rod, stick, dowel, etc (my metal rod came from Bioquip and cost around $8, but anything long and roundish that’s reasonably comfy to hold will do.  Avoid things that might give you splinters!)
  • duct tape (any project worth its salt involves duct tape, so you know this is gonna be good!) or waterproof tape

Okay, you’ve gathered your equipment.  Now let’s put the net together (here comes the complicated step):

 

soup strainer

Completed net. (Note: the duct tape on the handle is there to identify this as my strainer when I'm out with my students on field trips. It has no other function.)

Congratulations!  You now have a really great little net for catching aquatic insects!

I’ll admit that people scoff at my soup strainers and I get laughed at when I strap several of them onto my fishing vest.  Granted, I do look like some sort of deranged Kitchen Rambo stomping around in streams and ponds.  However, regardless of how dorky you look as you strain a pond or stream, soup strainers make fantastic aquatic insect nets!  For one thing, they’re cheap.  Look for sales and you can frequently get all metal strainers for less than $10 at stores like Target, Wal-Mart, and Ross.  Cheap is good.  If one breaks, simply chuck it in the recycling bin and start using a new one.  If you lose it, who cares?  The metal mesh also doesn’t get ripped the way aquatic nets do, so they’re super durable.  Soup strainers are lightweight, so you can carry several with ease.  I have a carabiner hooked onto my fishing vest that I loop through a couple of strainers when I’m out in the field.  And, they’re easy to use.  Trust me – it’s hard to beat a soup strainer for collecting aquatic insects.  I have a fancy aquatic D-net and I hardly ever use it.  Instead, I use my soup strainers.

There are 2 downsides to using soup strainers though.  One is that the mesh size is large, so sometimes it is best to use the more expensive “official” aquatic insect net, especially if it is important to know the number or diversity of insects you pull out of the water.  The other downside to soup strainers is that they’re short, so you have to get your hands wet to use them.  That’s not so bad if you live in AZ and the water rarely gets down below 40 degrees.  I lived in Colorado for a long time though, so I know there are places and times of the year when you really don’t want to stick your hands in the water.  That’s where the optional equipment comes in!  Here comes another complicated step.  Cut off a 12-15  inch long piece of duct tape and tape the handle of your strainer to your longish, roundish, pole-like object:

strainer with extension

Strainer with extension

Tada!  Now you’ve got yourself a nice long handle that keeps you well away from the water and allows you to collect in deeper water without getting wet.  You’ll need to replace the tape occasionally, but you’ll get a lot of use out of your MacGyver’ed soup strainer before you do.  If you spring for a more expensive roll of waterproof tape, it will last a lot longer.

Using your strainer is easy!  In a stream, hold your strainer in the water so that it is downstream of the area you wish to sample.  Stir the substrate up, either with your other hand, your foot, or with the front edge of the strainer.  Let the loose material flow into the strainer bowl, pull the strainer out of the water, quickly sift through the material in your net, and pluck the insects out!  (I recommend using feather forceps for handling aquatics as a lot of them are very soft-bodied and you don’t want to crush them.)  Dump whatever’s left back in the stream.  You’ll use a similar substrate-stirring technique in ponds, but you’ll have to sweep the net through the stuff you stir up because there’s no flow.  If you get a bunch of muck in your strainer, simply hold your strainer at the surface, half in the water and half above the water, and swish it gently back and forth.  The silt and other small debris will flow out of the strainer and leave the bigger things behind.

I know, I know.  It sounds completely stupid.  But it works!  I’ve handed soup strainers to well over 100 people in the last few years and I’ve won a lot of converts.  It’s amazing what you can collect with them.  Considering the price, the ease of transport, and the ease of use, you can’t go wrong.  I use mine all the time!

Me collecting in Florida Canyon

Me collecting in Florida Canyon with my trusty soup strainer!

Happy collecting!

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Print, save, or e mail this tutorial in PDF format!  Click on this link and the PDF will appear in a new tab or window.

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

Friday 5: My Favorite Insect Books for Kids and Pre-Teens

I liked making my list of books last week, so I’m going to continue the theme this week by focusing on children’s books.  I love children’s books!  I don’t have kids and all of my friends with kids live far away from me, but I still love to wander through children’s book aisles and see what they have to offer.  Children’s books have a way of condensing important concepts down into easily digestible chunks that I find admirable and I think everyone should read them.

Kids often LOVE insects, so there are tons and tons of great insect books out there for kids and pre-teens.  Here are five of my favorites from my own collection!

Children’s Classic: The Very Hungry Caterpillar by Eric Carle

The Very Hungry Caterpillar by Eric CarleWho doesn’t love The Very Hungry Caterpillar?  I was hooked on this book when I was a kid, and now I give it to my friends as a baby gift so they can share the love with the next generation.  I think it’s brilliant!  The illustrations are outstanding, the text is perfect for young kids, and there’s an educational message to boot.  Eric Carle is beloved by millions of children for a reason: his books are darned good!  If there’s one children’s insect book everyone should have in their collection, it’s this one.  (Carle wrote several other entomologically themed books as well, so I encourage you to check them out!)

Insect Poetry: Joyful Noise by Paul Fleischman

Joyful Noise by Paul FleischmanThis book is a ton of fun if you’re a kid!  It was released when I was in 5th grade, so I was just the right age to fully appreciate it when it was first given to me.  Joyful Noise is a collection of lovely Newbury Award winning insect poems accompanied by drawings.  What makes this book better than your average insect poetry book is that the poems are meant to be read aloud – and by two people.  In my experience, you really need to practice with your poetry partner to pull one of these poems off well, but trying is half the fun!  And, you don’t even realize you’re learning something in the process.

Great Insect Art for Children: Song of the Water Boatman by Joyce Sidman

Song of the Water BoatmanThis is my absolute favorite book for kids!  A friend of mine told me about it while we were in the field collecting insects for the National Park Service.  I knew I had to have it and I hunted it down the moment we returned to civilization.  I was instantly smitten!  Like Joyful Noise, this book is full of poems, this time focusing on aquatic animals.  But this book is ultimately my favorite children’s book because it is full of complex and expertly executed woodcut prints as illustrations.  Woodcuts and linocuts are among my very favorite art forms, so I think the illustrations make this book phenomenal.  And I’m not the only one – Song of the Water Boatman won a Caldecott Medal for its illustrations, securing its place in history as one of the most spectacularly illustrated books ever!  The poems teach kids about life in ponds and feature a lot of information about aquatic insects.  As you might imagine,  I rarely come across a book that combines my passion for aquatic insects with my love of woodcut art prints, but this book accomplishes it spectacularly.  Buy it, read it, love it.  Send it to your friends and family with nature loving kids.  I certainly do!

Insect Crafts for Kids: Crafts for Kids Who Are Wild About Insects by Kathy Ross

Crafts for Kids Who Are Wild About InsectsImagine that you are doing an outreach activity for kids that involves insects, or going to your child’s classroom to teach them something about science using insects.  You need a hook, something to get them really into the subject.  How about having them make the sucking mosquitoes from pipe cleaners, googly eyes, and eye droppers featured in this book?  I’ve been into crafts since I was about 4 years old and I’ve read hundreds of craft books for both children and adults over my lifetime.  As far as I’m concerned, this is THE best insect craft book for kids.  It’s great because it is full of wildly creative craft ideas that require only simple materials, are easy for almost any kid to do (that kid in the back who eats glue and can’t draw a straight line? He can make the things in this book!), and are surprisingly educational.  And kids love to make the things in this book!  I might not have my own kids, but I’ve done a ton of outreach activities with all ages of children.  The crafts in this book are a huge success every time I incorporate them into my sessions.  I highly recommend it!

For Older Children or Pre-teens: There’s a Hair in My Dirt! by Gary Larson

There's a Hair in My Dirt!Yes, THAT Gary Larson, creator of the entomologist-beloved The Far Side.  And because it’s Larson, save this book for older children or pre-teens.  This story isn’t about insects, but it does feature another invertebrate, the humble earthworm.  The narrative is quite cute and innocent on the surface, but it has darker undercurrents that are wickedly pro-environment and vividly illustrate the reasons why its necessary for humans to understand our world.  It also highlights the ecosystem concept, how things in an environment tie together with each organism playing a specific role, and illustrates how things can go terribly wrong if humans interfere.  The story is a little dark, but it makes some excellent points that everyone should acknowledge.  I use excerpts from this book to explain ecosystem concepts to nearly everyone – kids, teens, and adults.  It’s clever and entertaining, but it teaches you something very valuable about the world in the process.  And, it’s done in Larson’s signature style, so you know it’s going to be good!

There are so many other great insect books for kids out there that I might have to do another post on the subject.  For next week’s Friday 5, however,  I’ll get away from the literature and head back into the realm of insects.  I hope you’ll check back!

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

Hellgrammites

We had an insect trading session in the class I’m TAing this semester, so everyone brought in extra insects they had in their collections to trade for things they didn’t have.  I’m going to discuss some of my observations about the trading session in an upcoming post (I was fascinated!) but today I’m g0ing to focus on the specimen I was most excited about: a live hellgrammite.

Hellgrammites are the larvae of the insect known as the dobsonfly and they are fabulous (or at least I think so).  In their adult form, dobsonflies are pretty gnarly looking.  Males tend to have long, intimidating mouthparts:

Dobsonfly male

Dobsonfly male. Awesome photo by Jessica Lawrence, available at http://bugguide.net/node/view/ 419853/bgimage

Though the mouthparts look scary, they’re really pretty wimpy.  The males of most species can only inflict a minor pinch because the mouthparts are so large they can’t get any leverage on them.  But these giant mouthparts do have a purpose – and, as in most cases where insects have supersized body parts, it all comes down to sex.  Female dobsonflies size up potential mates according to the size of his mouthparts, and in the world of the dobsonfly, bigger is definitely better!  The males with the biggest mouthparts are the sexiest, most desirable males, so some dobsonflies have evolved truly massive ones.

So a male with giant mouthparts mates with a female with more reasonably sized mouthparts to produce eggs.  Those eggs then hatch and these crawl out:

Hellgrammite (Corydalus cornutus)

Hellgrammite!

Now I love hellgrammites and find them completely fascinating.  I am always thrilled to find these in the streams I work in and I can spend hours watching them.  Even so, I’ll be the first to admit that these are some truly vile looking larvae.  They’ve got big, strong mandibles they use to rip apart their prey and they are formidable predators.  They’ve got a pair of hooks on each of two fleshy prolegs on the back end (more about these in a moment) that stick to your fingers or clothes like burrs.  They’re big larvae too.  The hellgrammite in the photo is nearly 3 inches long!  And then there are the long, spindly gills sticking off the sides of the abdomen that give them an alien look.  These do nothing to diminish their threatening appearance and I think it makes them look like big, aquatic centipedes.

But those hooks and gills are also part of why I love hellgrammites.  If you’ve kept up with my blog, you know that my research broadly involves respiratory behaviors of aquatic insects.  Judging from the adaptations hellgrammites display and the habitats they live in, they need a lot of oxygen to survive.  That’s where the hooks and the gills come in: they both help the hellgrammite get as much oxygen from the water as possible.

Let’s consider the hooks for a moment.  If you’re an aquatic animal that requires a lot of oxygen, there is a specific type of water that is best suited to your needs: cold, turbulent, fast flowing streams or rivers.  That’s exactly where you’ll find hellgrammites, clinging to rocks right out in the areas of the strongest flow in cool or cold streams.  However, a giant three-inch long larva, even a flat one like a hellgrammite, is going to have a hard time holding onto the rocks when there’s water slamming into it constantly.  So, they’ve got these:

hellgrammite hooks

Prolegs and paired hooks at the posterior end of a hellgrammite.

Those little hooks grab a hold of the rock so that they aren’t ripped off the substrate and washed downstream.  Hellgrammites are also usually found under big rocks in these fast flowing streams, so the currents they experience are weaker than those on the upper surface of the rock.  Those little hooks aren’t always enough to keep a large hellgrammite in place if they venture out onto the top of the rock.

Hellgrammites are highly adapted for collecting oxygen from the water as well.  If you recall from my post on aquatic insect respiration, insects living in turbulent, cold water maximize their opportunities to collect oxygen from the water.  If they expand their exoskeleton into gills, their surface area increases and they can absorb as much of that relatively abundant oxygen as possible.  Hellgrammites have a lot of extra surface area in their gills.  The feathery looking gills sticking off the sides are rather immobile and simply increase the surface area.  The other set of gills, the puffy dandelion fluff looking ones, have muscles attached to them.  When a hellgrammite become oxygen stressed, it can wave those gills around through the water:

Waving the gills around is a form of ventilation and allows the hellgrammite to extract as much oxygen from the water as possible, especially under less than ideal situations.  The gill movements stir the water around the hellgrammite, pushing deoxygenated water away from the body and bringing oxygen-rich water into contact with the gills so that it may be absorbed.  Behavioral ventilation of this sort is common in aquatic insects and gill movements like this have been recorded in several species, especially within the mayflies.  Still, I can’t help but marvel at just how beautiful the hellgrammite gill movements are!  I hadn’t ever seen this behavior before I noticed it in the insect trading session and I was amazed.  I found it shocking that something that ugly could also have such a stunning characteristic.  It was almost hypnotic watching the hellgrammite pulsing its gills and I could have watched it for hours.

But then I was snapped right out of my gill-inspired reverie when the hellgrammite started to swim around the jar:

I don’t know about anyone else, but I find this sort of abdomen flicking, backwards swimming kinda creepy.  Crayfish do it too and it’s just bizarre.  Doesn’t that look like rather inefficient way to maneuver around your environment?  I can’t easily come up with a reason why this sort of swimming would have developed, though I’m sure there’s a good explanation.

Yep.  Hellgrammites are appalling to look at, but they are amazing in so many ways that I have to love them anyway!  I hope I’ve given you at least a little taste of my appreciation for these monsters of streams and rivers.  I’ll probably describe my plan for making a horror movie called “Hellgrammite!” at some point in the future.  I am sure you are all eagerly looking forward to hearing all about it.  It’s going to be fantastic!  :)

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