Wordless Wednesday

A friend of mine told me about Wordless Wednesday today.  For those of you who don’t know what this is (like me before today!), many bloggers put up posts with images, but no text, on Wednesdays.  People can search for Wordless Wednesday to see a wide variety of images and find new blogs.  I’m going to start participating.

My first offering:

Hellgrammite (Corydalus cornutus)

Hellgrammite (Corydalus cornutus)

_______________

Image copyright © 2009 DragonflyWoman.wordpress.com

Advertisements

Bugs in the Movies: Miniscule

This past week has been crazy busy and I’ve barely had time to think, let alone write in my blog.  Sorry it’s been so long since I last posted something!  I really love working on my blog, so I find it sad when I can’t do it as often as I’d like.  Rather than launching into the subject of giant water bug parental care or going over how to ID the dragonflies I saw at Sweetwater Wetland as planned, I’m going with a lighter post today.  Grab some popcorn and settle in – it’s movie time!

If you’ve perused my links, you might have noticed the link to Miniscule, maybe even wondered what it is.  Miniscule is far and away my favorite source of entomologically-themed animated movies!  The movies are short, on the order of 5 minutes long, but they are brilliant.  The French team that creates the movies, about one a month, combines fantastic macro video of natural settings and 3-D animations of insects and other creepy crawlies.  The videos are silent films and rely entirely on their visuals to convey their stories, but they are reasonably accurate in their entomological details.  They are also darned cute.  So, without further ado, I present my favorite of the Miniscule movies so far – a film about a snail with dreams of greatness!

_______________

Text copyright © 2009 DragonflyWoman.wordpress.com

Color Polymorphisms in Dragonflies

In my last post, I talked about the dragonflies that my fiancee and I saw on our recent photographic trip to Sweetwater Wetland in Tucson.  We took a lot of photos of dragonflies and as I went through them, it occurred to me that there is an important topic related to identifying dragonflies that I have not covered so far in my blog: odonate polymorphisms.

If you’re like most people (including me until I’d been an entomology grad student for almost a year), you’re now thinking to yourself, “what is a polymorphism?”  You probably already know more about polymorphisms than you might think!  First, let’s take apart the word to define it.  The root “poly” means many.  Think back to geometry and polygons – a polygon is a shape with many sides.  The root “morph” means shape or form.  So, the word polymorphism effectively means “many forms.”  Form can refer to shapes, colors, sizes, and other characteristics of biological organisms that might vary between stages, sexes, or individuals within the same species.

You probably know about a few species that exhibit polymorphisms already.  Birds are a classic example of sexual dimorphism (di = two, so dimorphic species exhibit two forms): males take one form while females take another.  In birds, the males are often one color while the females are another.  In most cases, the males attract the females, so the males are the more colorful, showy individuals.  In general, the more brightly colored males are healthier and better able to produce strong offspring with a high chance of survival, so females will choose mates that are brightly colored over less colorful males.

Peacock and peahen

Peacock and peahen

As an example, consider peacocks.  Peacock males are VERY showy with their long, elegant tails while the female peahens are much less colorful and have much shorter tails.  Peacocks with the biggest, baddest tails get all the girls while the less showy males have to settle for leftovers (sometimes younger or less healthy females) or simply cheat their way into getting a mate.

Other animals that show dimorphisms are deer and elk.  Again, the males are trying to attract the females and are willing to fight other males for them.  Elk or deer with big racks are generally better able to successfully fight other males.  As in birds, the buck with the biggest rack is likely healthier than the bucks with smaller racks – they have to be getting enough food and other resources to grow those antlers in the first place.  The doe chooses her mate from the available males and usually selects the one that is best able to win fights, the one with the best antlers.  Because the females are not fighting amongst themselves and are not trying to attract the males, a doe doesn’t need antlers.  So, some elk and deer have horns (the males) and others do not (the females).  They are also sexually dimorphic.

Now let’s get back to the dragonflies.  Like in birds, elk, and deer, it is the role of the male dragonflies to attract female dragonflies if they wish to produce offspring.  Thus, male dragonflies are often much more brightly colored than the females and many species are sexually dimorphic.  Take, for example, the blue dashers, or Pachydiplax longipennis.  If you follow my blog, you’ve seen this one before, but here he is again in all of his elegant glory:

Blue dasher (Pachydiplax longipennis) male

Blue dasher (Pachydiplax longipennis) male

Blue dashers are very common mid-sized dragonflies across a big section of the United States, including Arizona.  The males are easy to identify based on their bright green eyes and the bluish coloration of their bodies.  The abdomen is covered in a waxy substance, or prunescence, which can give them a bit of the whitish look you see in the male pictured here.  Blue dashers are perchers, so you’ll commonly find the males sitting on emergent vegetation or on bushes and/or other plants alongside lakes and ponds.  They sit and guard their territories from their perches, waiting for females to come into their areas so they can mate.  In contrast, the females are known to spend a much greater part of their time away from water and only come to the water to mate and lay eggs.  I found this female sitting on a tree branch far from the water:

Blue dasher (Pachydiplax longipennis) female

Blue dasher (Pachydiplax longipennis) female

Can you see how different the female looks compared to the male?  The males are a whitish bluish color while the females are largely black!  The female blue dashers are about the same size and of similar shape compared to the males, but they have very different body colors, making this a dimorphic species.  Female blue dashers are also very easy to identify.  Just look for a black abdomen with yellowish or brownish stripes on each section of the abdomen.  The abdomen tends to be a bit stumpy compared to the male abdomen, so the wings look disproportionately large.  In fact, this is the origin of the species name longipennis, which means “long winged.”

Blue dashers are considered dimorphic because there are two main forms, but they are not exactly sexually dimorphic either.  Odonates are not sexually mature when they molt from nymph to adult and require a period of a few days to complete their maturation.  Immature individuals, including the males, look like the females.  So, the mature males are blueish and the immature males, immature females, and mature females all tend to look like the picture of the female.

Many dragonflies and damselflies follow similar patterns.  Green darners (Anax junius) are actually polymorphic:

Anax junius mating pair

Green darner (Anax junius) pair

As you can see in the photo, the male (the dragonfly in front) is green and blue while the female is green and green-brown.  Immatures of both sexes can have a reddish abdomen and the females can have brown sections on their abdomen.  Sometimes the females even have about the same blue on their abdomens as the males!  Because the green darners have so many different color patterns, they are considered polymorphic.

Not all dragonflies exhibit dimorphism or polymorphism.  Some dragonflies are monomorphic (mono = one) such that all indviduals look about the same, regardless of sex or age.

Next time I’ll post some more photos from the Sweetwater trip and go over how to identify them.  I hope you’ll stay tuned!

_______________

Text and images copyright © 2009 DragonflyWoman.wordpress.com

A Trip to Sweetwater Wetlands

Before I get back to the water bugs, I want to continue my detour for a few posts and talk about some dragonflies I saw yesterday.  I needed to take some dragonfly photos, so my fiancee and I went to a constructed wetland in Tucson called Sweetwater to shoot.  Sweetwater is part of one of the wastewater treatment plants in Tucson and is fed entirely with reclaimed water and secondarily treated wastewater.  It can smell pretty bad at times (it IS made up of treated wastewater after all), but if you can overlook the scent it’s gorgeous and wholly worth a visit.  All those nutrients in the water do wonders for the plant life that grows in the water:

Sweetwater Wetland

Sweetwater Wetland

As you can see, the nutrient-rich water of the wetland is able to support a wide variety of aquatic plants.  Yesterday, the wetlands were full of cattails (the dark green bushy looking things on the right side of the picture), rushes, sedges, and duckweed.  Most of the bright green stuff floating on the water in this picture is duckweed, NOT algae, though there was definitely algae there as well.  The wetland also suports a variety of trees and shrubs and many different species of wildlife.  All those dark spots in the picture are ducks.  I’ve also seen several snakes and lizards, many other birds, and even a bobcat once!  And then there are, of course, the dragonflies.  Thousands of them.  I think Sweetwater is the best place in Tucson to see dragonflies.

We saw several dragonfly species, including green darners (Anax junius), arroyo darners (Aeshna dugesi), blue-eyed darners (Rhionaeshna multicolor),  flame skimmers (Libellula saturata), roseate skimmers (Orthemis ferruginea), blue dashers (Pachydiplax longipennis), Mexican amberwings (Perithemis intensa), variegated meadowhawks (Sympetrum corruptum), and black saddlebags (Tramea lacerata).  We also saw one species of damselfly (though we weren’t really looking hard for the damselflies either – there may have been more), the desert firetail (Telebasis salva).  Most of the dragonflies were flying above the cattails or were resting on them in various positions.  Some were even in the obelisk position, which I have talked about before in another post on dragonflies.

I got some good shots of several different species, which I’ll go over in my next post.  However, I was most thrilled with all of the large flying dragonflies, the darners.  I like taking pictures of flying dragonflies the best because they are the hardest to shoot.  This is the same reason I got interested in dragonflies in the first place – catching dragonflies for my collections for 4-H was the biggest challenge.  I have yet to get a really, really good shot of a flying dragonfly, but I keep at it, and I got some pretty decent shots today.

This is Anax junius, the green darner:

Anax junius mating pair

Anax junius mating pair

This is a mating pair.  The male, the more brightly colored one with the blue abdomen, had just grabbed his mate in preparation for mating, and then they promptly fell out of the tree onto the sidewalk, right next to me!  They sat there in this position for almost a minute while I snapped away with my camera.  Then they flew off to mate and lay eggs.  Anax junius was very abundant at Sweetwater yesterday, so I ended up getting a lot of pictures of them.  They are fliers, so they don’t land very often.  That also makes them fairly hard to photograph – they don’t sit still for very long.  So, most of the photos I got were of these insects flying, and most of them looked like this:

Dragonfly photo

Typical dragonfly flight photo

The little smudge in the photo at the tip of the big blue arrow is the dragonfly!   I took about 90 photos of Anax in flight, and these were the best:

green darner in flight

green darner in flight

green darner in flight

green darner in flight

green darner in flight

green darner in flight

What I particularly liked about these images, aside from the fact that they are actually mostly in focus, is that you can see the legs of the dragonflies folded up underneath their thoraxes.  Having the legs folded up under the body likely helps the dragonflies fly more efficiently.  If they let their legs dangle down underneath them, they are likely to slow the dragonflies down, get snagged on the vegetation when they fly low, and otherwise cause problems.  So, they fly with them tightly folded under their bodies and only stretch them out when they grab food in midair.  It’s fun to be able to see that they do this, but it would be hard to see by observing them directly because they fly so fast and so erratically.  It’s easy to see in the photos.

Like in my post on the species from the dragonfly swarm, you can clearly see from these photos that dragonflies are able to move all four of their wings independently from one another.  For example, in the top photo, you can see that the forewings are both moving down while the hindwings are moving up.  This ability to move their wings independently contributes significantly to the amazing agility that dragonflies exhibit.  If you’ve ever seen dragonflies flying, you know how fast and agile they are.  They can stop in midair, make 180 degree turns, fly backwards, hover, and do all sorts of other things that are nigh impossible for most flying animals.  They dart all over the place, which is why it’s hard to get photos of them in flight.  If you’re dealing with a flier species, such as Anax junius, they are going to be moving constantly too.  Another reason it’s hard to get good photos of dragonflies in flight is the behavior you see in this photo:

green darners in flight

green darners in flight

Dragonflies are highly territorial and protect their territories from other dragonflies that might be trying to steal their access to prime egg laying habitat or other valuable resources.  In flier species, the males typically patrol, or fly within the boundaries of their territories, looking out for females to mate with, food, and males who might want to try to claim the territory for themselves.  In this photo, the dragonfly at the top tried to steal the territory that belonged to the dragonfly on the bottom.  The owner of the territory, the dragonfly on the bottom, successfully chased the would-be thief out away from his territory.  In the photo, the territory holder is returning to his territory to continue patrolling while the loser is flying away to find another spot, hopefully one guarded by a wimpy male.  Because there are usually fewer territories available than dragonflies at a pond, these battles are constantly occurring.  When a male sees another male that might enter his territory, he will immediately change directions and charge the tresspasser in an attempt to protect his territory.  This means that the dragonflies are darting back and forth constantly.  You might track one dragonfly and just be ready to snap a photo when he stops, turns around, and zips off in a completely diferent direction.  It’s very hard to predict where a dragonfly is going to be at any given time, so it is difficult to get good photos of them in flight.

Next time I’ll go over how to identify some of the species that we saw at Sweetwater, then it’s back to the giant water bugs for a while!

_______________

Text and images copyright © 2009 DragonflyWoman.wordpress.com

The sting

Before I get to posting about the giant water bug parental care behaviors, I thought I might make a small digression and talk about an encounter I had with an insect a few days ago.  Now, I apoligize in advance for this not-so-appealing photo, but this is what my foot currently looks like:

my foot

my foot

See the big red spot in the middle?  I got that from an insect!  Three days ago!  The ants that have taken over my house (you can read more about them in my ant post) have now apparently invaded my closet and one of them got into my shoe.  I never think to check my shoes before I put them on (stupid, really, considering where I live), and the ant wasn’t all that thrilled that I was apparently trying to smash it by putting my foot inside my shoe.  I wouldn’t have known it was even there except that I felt a few familiar, sharp stinging sensations on the top of my foot and ripped the shoe back off.  Sure enough, out wanders this one tiny little Brachymyrmex ant.  That’s right – that welt in the photo, which is about a half inch in diameter and both itchy and painful, was caused by a 2mm ant stinging me!

Today I thought I might talk about ants and the common misconception that the pains that people experience when they encounter ants are bites.  Lots of ants do bite, but they simply have big jaws (or not so big in the case of Brachymyrmex!) and all they can do with them is pinch.  Ant bites don’t involve venom (a poison that is used to subdue prey or deter a predator), so the pain from a bite is short lived.  At most you’ll get a nice little red spot that quickly goes away.  The real pain, and any long term swellings or other allergic reactions, come from ant stings, not bites.

Let’s think about how another insect we’re more familiar with, the honey bee, stings.  Honey bees are well known for their stinging, especially if their hives are disturbed, and even more especially if they are aggressive Africanized (or killer) bees.  Honey bees have a long, serrated stinger that they inject into the skin of whatever is disturbing them.  They have venom sacs at the base of their stingers which pump venom through the stinger into the animal being stung.  This venom causes a lot of pain.  However, honey bees are a bit of a special case.  Because they have the serrated stingers, the stingers tends to stay inside the victim.  It’s basically a one way system, like a fishhook or some cactus spines, in that the stinger can be inserted easily, but the serrations keep the stinger from being pulled back out.  The bees are usually unable to pull their stingers back out of their victims and the whole back end of the bee will often rip off with the stinger, eventually killing the bee.  (There are some great photos of bee stingers and stings on the Wikipedia article on bee stings!)  In honey bees, stinging is effectively a suicidal action – most honey bees that sting do not live to sting again.  However, leaving the stinger behind is also an excellent deterrent.  Until the stinger is pulled out or runs out of venom, it is able to keep pumping painful chemicals into the victim.  For honey bees, the risk of death is worth the use of the stinger.  Most animals will be deterred by the pain of the stings they receive if they disturb a honey bee nest and will stop their attack before they destroy the honey comb or the queen.  Honey bees sting to protect their resources from other animals that might want to steal from them, and those resources are important enough to the colony as a whole to risk dying to protect them.

Ants and many wasps are similar to honey bees: they all have stingers and venom sacs.  Ants and wasps tend to have smooth stingers though, so they are able to pull their stinger out of their victims intact and may sting more than once.  This is something I experienced with my ant sting.  I was actually stung in 3 different places, though only the sting in the photo involved enough venom to leave a lasting mark.  Ants and wasps use their venom for many different reasons, ranging from protecting their nest or themselves (like in the honey bees) to immobilizing prey items or host organisms.

So just how do stingers work?  First, let me share a fun fact: all bees, ants, and wasps that sting are female.  That’s right – males don’t sting!  This is the case for many biting and/or stinging insects actually, but particularly so in the Hymenoptera.  Consider then what females have that males do not.  Any ideas?  If you thought about the differences in their reproductive systems, you’re on the right track!  Many insects have external (and sometimes retractable) tubes through which eggs are laid.  These tubes are called ovipositors.  The hymenopterans have evolved a further use for their ovipositors – a venom delivery device.  Some hymenopterans, like some of the ichneumonid wasps (wasps that have REALLY long stinger looking things coming off the back!), use their ovipositors to drill into wood, locate beetle larvae or other insects that are already inside the wood, immobilize the insect larvae with their venom, and then lay eggs on these prepared host insects.  In these insects, the ovipositor is used as both a egg delivery tube and a venom delivery tube.  The ants and many of the bees have evolved a second tube that is now used specifically for eggs, leaving the original ovipositor to act solely as a stinger.  Males do not lay eggs, so they do not have ovipositors.  Because they do not have ovipositors, they never had the equipment necessary to develop stingers.  So, all stinging hymenopterans are female.

That means that the ant that stung me was a female.  As were all of the hundreds of other ants that have stung me in my lifetime.  I seem to be particularly attractive to ants and get stung all the time!  Unfortunately, I believe I am becoming sensitized to ant, bee, and wasp venom as well.  Some people start developing sensitivities to hymenopteran venom over time, especially when they are stung often as I am.  When I was a child, ant, wasp, and bee stings left only little red marks that usually went away within a day.  The last time I was stung by a wasp, I had a horrible reaction, a swelling that ended up about the size of a dinner plate that was rock hard.  And the last few ant stings I’ve gotten have given me the big welts you saw in the photo.  This likely means I’m becoming sensitized – I’m having stronger and stronger reactions every time I get stung.  Not all people become sensitized to venomous hymenopterans and some people will have the same reaction every time they are stung through their entire lives.  I am unfortunately not one of these lucky people and might end up needing to carry an epi pen with me in the future in case I get stung and go into anaphylactic shock.  Not a happy thought, but there’s nothing I can do about it either.

In the meantime, I have to wear shoes that don’t touch the welt on my foot so it will heal more quickly and doesn’t hurt so much.  And I’ll also start looking in my shoes before I put them on!  At least until the ants find a better place to live than my house and move on.  I’m really looking forward to that day…

_______________

Text and images copyright © 2009 DragonflyWoman.wordpress.com