Swarm Sunday – 1/1/2012 – 3/18/2012

Dragonfly Swarm Project logo

I’m back!  I was sorry to drop off the face of the Earth last week because I always miss blogging when I’m not able to do it, but I needed to spend some time with my husband away from work.  But now I’m back!  Hopefully you all had a great week without me.  :)

Today I’m going to do the first Swarm Sunday post for the year!  I haven’t been deluged by reports or anything, but there has been some very early activity this year.  Since New Year’s, I’ve received the following reports:

USA:

Fort Pierce, FL
Vero Beach, FL
Saint Augustine, FL (2 swarms)
Hudson, FL
Naples, FL
Edgewater, FL
Sarasota, FL
Oakhill, FL

Australia:

Melbourne, Victoria

Clearly, Florida is the place for dragonfly swarms recently!  There is a fair amount of early activity happening there, as early as Mid-February.  Could this be part of the spring migration back north?  Interestingly, not all the dragonflies reported have been green darners either as the black saddlebags have made an appearance too.  Very interesting…

In other dragonfly swarm news, the Migratory Dragonfly Partnership is gearing up to start collecting detailed data on dragonfly migrations!  There are going to be many ways that you can help out, including citizen science projects you can get involved in, so I’ll keep you posted as more things go online.  I’m excited to be a part of this partnership and I know you all can contribute some valuable information to the MDP.  For now, the website is quite spartan, but things will he up and running soon!

I’m looking forward to year three of the Dragonfly Swarm Project!  Keep the reports coming.

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Have you seen a dragonfly swarm? I am tracking swarms so I can learn more about this interesting behavior.  If you see one, I’d love to hear from you!  Please visit my Report a Dragonfly Swarm page to fill out the official report form.  It only takes a few minutes! Thanks!

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Want more information? Visit my dragonfly swarm information page for my entire collection of posts about dragonfly swarms!

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

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Friday 5: Aquatic Insects that Suck

For today’s Friday 5, I’m going to discuss five aquatic insects that suck.  No, not that kind of sucking!  These are insects that have suction cups, or suction cup-like structures, that allow them to live in their aquatic habitats.  Now I don’t know about you, but I find it pretty amazing that there are insects with suction cups on their bodies, so I feel the need to share the love!  In no particular order, I present 5 aquatic insects that suck:

water penny

Water penny, top view

water penny

Water penny, bottom view

1. Water pennies.

Water pennies are funky insects – and yes, that IS an insect!  As adult beetles, most species aren’t that exciting, just nondescript black beetles.  But the larvae, pictured here, are bizarre!  These insects don’t have suction cups on their bodies like most of the other insects on my list today.  Instead, their whole broad, domed shaped bodies work like suction cups!  I’ve written about how water penny larvae work before, so I won’t go over it in detail again here.  However, if you think of the little plastic suction cups you use to stick things onto windows, you’ll have a pretty good idea of how the suction works.  You’ll find these living on the tops of rocks in cold, fast flowing streams.

Blepharicerid larva, top

Net-winged midge larvae, top

Net-winged midge larvae, top

Net-winged midge larvae, bottom. The dark, round discs are the suction cups.

2. Net-winged midges.

Ah, blepharicerids.  I can remember the first moment I found one of these in a stream.  I nearly yelled out in utter joy!  It’s one thing to see pictures in a book and quite another to find hundreds of them all over rocks in a stream.  These fly larvae are truly amazing.  They’re bizarrely shaped, even by insect standards, with constrictions along the length of the body.  Each constricted section also contains a suction cup.  Like the water pennies, they live right out on top of rocks in cold, fast flowing streams, so they’re constantly being slammed with water as it flows downstream.  The suction cups keep them from being swept away!  (If you think the larvae of these flies are interesting to look at, I highly recommend that you take a look at the pupae.  Weird!)

predaceous diving beetle

Predaceous diving beetle (Thermonectus nigrofasciatus)

dytiscid foot

Predaceous diving beetle foreleg. The suction pad is made up of several individual suction cups.

3. Predaceous diving beetles.

These are the only adult insects I know of that have suction cups.  And, they don’t use their suction cups to prevent their washing downstream like most aquatic insects with suction cups.  Any idea what they might be used for?  Hint: only the males have them.  These suction cups are used during mating!  Predaceous diving beetles are extremely well adapted for swimming and exhibit very smooth, domed bodies that allow them to move through the water with surprising grace.  If you’ve ever tried to pick one up with forceps, you know how slippery these little buggers are!  This causes problems when a slippery dome-shaped male wants to climb onto his slippery domed-shape mate’s back and get down to business.  So, they evolved suction cups on their forelegs!  You can see them there in the photo – lots of little suction cups making up a big suction pad.  The male presses the suction pad onto the female’s back and is able to hold on long enough to mate.  Pretty neat, eh?

Rhithrogena impersonata

Rhithrogena impersonata. Photo from http://www.troutnut.com/specimen/482.

Rhithrogena impersonata

Rhithrogena impersonata, bottom. Photo from http://www.troutnut.com/specimen/482.

4. March brown mayflies.

Mayflies in the genus Rhithrogena (family: Heptageniidae)  are rather similar to the water pennies in that they do not have true suction cups.  Instead, they have flat bodies and their abdomens are ringed by broad, flat gills.  The space between the gills works like a suction cup and keeps these mayflies attached to the rocks on which they live in streams.  While these nymphs are not dome shaped like the water penny larvae, their suction cup works in a similar manner.

Leech

Leech. Leech sucker is inset.

5. Leeches.

Leeches are not insects.  In fact, they’re not even arthropods!  However, they are aquatic and they definitely have suction cups, so I’m including them in my list.  Leeches use their suction cups to grab the substrate or to hold onto their prey as they suck their fluids.  I also personally think they add to the overall distasteful appearance of these animals.  I mean, what’s not to love about an animal that uses a sucker at one end to attach to you and a sucker at the other end to suck your blood?  :) (Okay, I’ll admit that I do actually like leeches.  Ever seen one swim?  It’s both horrifying and mesmerizing and I can’t tear my eyes away!)

Don’t know what I’ll do next week!  I have a long list of ideas, so it will depend on my mood when I sit down to write.  Maybe something Christmasy!

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

Insect Respiration

I’ll admit that I am a bit A.D.D. when it comes to biological research.  I find everything interesting!  This makes it hard for me to focus on one specific thing all the time, so I have a lot of little side projects going at most times.  (And if any of you are in grad school out there, this is NOT the way to finish quickly!)  However, if I were to say I had one specialty, insect respiration (particularly respiratory behaviors) is it.  So, it’s time to dive into the science of insect respiration!  The next 3-4 major posts will focus on several different facets of insect respiration (finishing up with another From the Literature post), but today I’m going to go over the basic system of insect respiration, the one you would find in most typical terrestrial insects.

human respiratory system

The human respiratory system. Image taken from Wikipedia: http://en.wikipedia.org/wiki/File:Respiratory_ system_complete_en.svg.

 

Humans have a rather complicated respiratory system.  We use our lungs to draw oxygen into our bodies through the nose and mouth.  Our lungs branch and branch and branch some more, and air travels down these branches until it reaches the alveoli, small air sacs at the very end of the lungs.  These air sacs are very thin.  The capillaries (part of the circulatory system) that run along the outside of the lungs are also very thin.  This allows oxygen to travel from inside the lungs, through the lung tissue, through the capillary tissue, and into the red blood cells inside the capillaries.  The red blood cells then carry the oxygen from the lungs to other parts of the body and deliver it to needy cells.  The human respiratory system requires both the lungs and the circulatory system to function.

Insects are much less complicated than this.  For starters, they don’t have much of a circulatory system.  They have a blood-like substance called hemolymph filling their bodies, but it tends to slosh around inside without a lot of direction.  If you don’t have a fancy circulatory system that directs blood into specific areas, you can’t depend on your blood to transport oxygen from the outside of your body to your cells.  So, insects use a different system.

insect spiracle

A spiracle on a caterpillar. The blue arrow points to the opening.

Most people know that insects are divided into three major body sections: the head, thorax, and abdomen.  You may not know, however, that these main body segments are made up of several subsegments.  The thorax is divided into three sections called the prothorax (pro means forward), mesothorax (meso means middle), and metathorax (meta means after).  The abdomen of a typical insect is made up of 11 subsegments.  So why do we care about these subsegments?  Because most or all of these subsegments contain a pore in the insect exoskeleton that allows oxygen to enter the insect.  These pores are called spiracles.  Take a look at the caterpillar image and you’ll see several of these spiracles running down the length of its body.  Many insects have muscles associated with their spiracles that allow the insect to open and close them on command.  Other insects leave them open all the time and some don’t have spiracles at all!  But most insects do, so we’ll focus on the ones that do here.

insect respiratory system

Diagram of a simple insect tracheal system.

Spiracles connect the air outside the insect to the inside of the insect where it is needed by the cells.  The spiracles connect to the tracheae (plural of trachea), big, open tubes that travel from the spiracles some way into the body.  The tracheae then branch again and again into ever smaller tubes.  At some point, the diameter of the tubes gets so small the tubes become tracheoles.  Air passes to the end of the tracheoles and is delivered to a single cell or a small group of cells, where it is taken in and used for necessary cellular functions.  So, unlike the human system where air is collected in the lungs and is then transported to cells via the blood, the insect respiratory system delivers air directly to the cells!

You may be wondering how air gets into that system of tunnels in insects.  Well, many insects don’t “breathe” the way that humans do.  Humans have a muscle called the diaphragm that causes us to take breaths as it contracts and relaxes.  While some insects do use their muscles and simple air sacs to actively pull oxygen into their respiratory systems, many do not.  These insect depend entirely on a property of physics called a concentration gradient.  A gradient forms when oxygen (or another gas or a liquid or a chemical or molecules) is in a lower concentration in one location compared to another, i.e. there are fewer molecules of oxygen in one place than another.  When concentration gradients form, molecules tend to move from areas of high concentration to low concentration to restore an equilibrium between the two areas.  This happens in the insect respiratory system.  The insect cells use the oxygen that has traveled down the tracheal system, so there is less oxygen at the end of the tubes than there is outside the insect.  So, molecules of oxygen pass into the tracheal system to replace the oxygen that was used and end up at the tips of the tracheoles.  These molecules are also used by the insect’s cells, so more oxygen enters the tracheal system to compensate.  Thus, oxygen continues to flow into the respiratory system and the insect is continuously supplied with the oxygen it needs to survive.  This same system also takes the carbon dioxide the cells produce back out via the same process in reverse.

What I’ve described here is a sort of basic, generalized model of insect respiration, and a terrestrial one at that.  There are many, many variations on this theme.  Some insects use what is called ventilation and actively pull oxygen into their respiratory system, such as those insects I mentioned above that use muscles and air sacs.  Other insects use a system called discontinuous gas exchange where they hold their spiracles shut most of the time and then open them quickly every now and again, likely to conserve water.  These insects sort of hold their breath and then take in big gasps of air only when they really need to.  Aquatic insects exhibit many variations on the basic insect respiration plan that allow them to breathe more efficiently in water.  These adaptations will be the focus of my next post, so I hope you’ll stay tuned!

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Text, caterpillar image, and tracheal diagram copyright © 2010 DragonflyWoman.wordpress.com