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Males Can Sniff Out A Well Fed Female July 8, 2011

Posted by Mrs Weird Scientist in Animals, Brain Power, Insects, Think About It.
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If they’re a male black widow spider, that is. Simply by taking a little saunter across the female’s web, a male black widow can sense if a female is hungry or not. Why does it matter? Because female black widow spiders have a rather freaky habit of eating the male after mating. It’s how they earned their dangerous name.

Now that’s one massive female black widow spider. You would almost think she’s been doing some seriously heavy weights at the gym. But nope, females are normally much bigger than males. Those males best watch out!

The Smell Of Safety

Males have developed this very useful technique, which tells them whether or not a female has recently eaten. But if a female is hungry, she would be more likely to cannibalize the male spider. They take a sniff of those silk strands and then decide if they want to proceed or scurry away. A new study discovered this interesting skill and published the findings in the journal Animal Behaviour. So, how do researchers actually go about testing something like this?

Feeding Time For The Ladies

First things first. The researchers fed a bunch of hungry female back widow spiders. Using a cricket neatly held between forceps, they rested it on the web and waited for the female to come over, wrap the cricket in silk and chow down. The females got one cricket each week. Yet, by the time the fourth week came around, they weren’t so hungry anymore and didn’t really want to eat the crickets.

I bet this female black widow spider is thinking: “Ah, the satisfaction from a good meal of crickets. I think I’ll accept the advances of the male spider perched nearby. Since I’m well fed, I probably won’t eat him after we’re done.”

Another bunch of female black widow spiders were starved for a few weeks. It apparently didn’t put their lives at risk, but they did get a bit smaller. Now, let’s find out what happened when a male was placed on the web of a well fed or a starved spider.

One Step, Two Step, Three Step…Four

Since the male spiders can pick up scents with their feet, they were able to figure out the difference from one female to another just by walking on the web. Normally, a male black widow spider has a special dance he does to court the female.

In this experiment, the males danced far more actively on the webs of well fed females. Smart dudes! If anything, dancing and mating would leave them ready to eat – not be eaten! Typically, they dance around for an hour or two, which sure shows their dedication to the purpose. They wave their legs and pluck and tap at the web in a unique way, so that unlike prey they show the female they are interested to mate rather than become dinner.

If Only I Had Such Powers

Now I have a strong sense of smell but definitely nothing like these male black widow spiders. It’s too bad because I’m really scared of spiders even though I know most are harmless. If I had my way, I’d be able to simply smell any spider from several meters away. That would give my timid self enough time to run!

How To Be An Assassin February 21, 2010

Posted by Mrs Weird Scientist in Animals, Brain Power, Insects, Think About It.
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Credit: Video generously provided by Anne Wignall of Macquarie University.

Imagine you’re a hungry insect. To get your next meal, you need to be a true assassin, using stealthy tactics to capture your prey. Well if you were an assassin bug, then your plan might read like this:

1. Slowly approach your prey

2. Tap the web before each step

3. Bounce around a bit

4. Grab some web strings

5. POUNCE

It might sound like a strange plan but it works! The assassin bug does all these bizarre movements to trick the spider into thinking it has an insect caught in its web. Once the spider is sure that it has its next meal, it scurries over to the assassin bug. But too bad for the spider, it will now become a tasty meal for this sneaky insect. To find out more about this peculiar bug, I chatted with Anne Wignall of Macquarie University in Sydney, Australia, who had some of her recent work published in the Journal of Ethology. Anne already knew that some bugs would hunt down spiders but she wanted to find out just how they did it! Anne explained to me:

When I heard that there was a bug that seemed to lure spiders toward them, I was instantly fascinated because it seems like such a crazy thing to do, when spiders are such dangerous predators themselves.

In fact, there is actually one more step in the assassin bug’s plan, which could come in at number six. Once the assassin bug grabs the spider, it sometimes will tap the spider with its antennae. Researchers think this might be a way to hypnotize the spider, making it harder to escape.

A World Of Assassins

The assassin bug in the video above is a species known as Stenolemus bituberus. But if you thought it was the only one, think again! Anne describes just how busy our world really is when you get outside:

There’s also lots and lots of other assassin bug species and insects that use stalking, deception, luring and other cool tactics to hunt other invertebrates, and we’re finding more all the time.

So this means there are way more bugs out there with incredible, assassin-like tactics to capture their prey. For example, Todd Blackledge of the University of Akron in Ohio has been investigating how wasps hunt spiders. He found that adult female wasps will capture spiders and sting them. Ouch! But that isn’t all. The wasp then lays an egg on the spider, which allows the wasp larva to eat the spider, helping it grow into an adult.

Your Garden: A Battleground For Bugs

Now that you’ve checked out the video above, you might actually be able to find one of these creepy crawlies in your garden. Anne suggests that if you live along the east coast of Australia, you should explore the trees and webs in your garden, where you might find an assassin bug battling it out with a spider. Just be glad that while those hungry bugs fight it out, you don’t have to go through anything quite so dramatic when you want to have lunch. In fact, make yourself a nice sandwich, grab your camera, then see what you can find in your backyard!

The Return Of Bed Bugs – Smarter Ones January 13, 2010

Posted by Mrs Weird Scientist in Animals, Evolution, Insects, Tough Stuff.
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10 comments

Your mattress may be home to more than your pillow or favorite stuffed animal. It could be the home of bed bugs!

The title reads like a horror movie but for those who have battled it out with bed bugs, it makes a lot of sense. Others might think that ‘don’t let the bed bugs bite’ was just some bedtime line their parents used as a cute joke.

In fact, let’s see now who knew that bed bugs really existed. Try out the poll below (be honest!).


Bed Bug Basics

Bed bugs are small, reddish brown insects that feed on human blood, which engorges them and makes them bigger. They are from the insect family Cimicidae and common bed bugs are formally called Cimex lectularius. They tend to be most active at night, coming out of the cracks in walls or bed frames and other hiding places to get their bloody grub. They can travel in suitcases, so hotels are a hot spot for bed bugs as well as other places that see plenty of people coming and going. Cornell University has an ace fact sheet to give you the lowdown on bed bugs. You can also have some fun playing around on Pest World for Kids, a website created by the National Pest Management Association (NPMA). But let’s get back to finding out why these wee pesky critters have returned and what makes them smarter today.

Gone But Not For Long

Here we have a bed bug hiding in a wood bed frame. The bed bug looks like it's having a Sunday snooze but I bet it's getting rest so it can hunt for fresh blood! Image credit: Thomas Oldani

Bed bugs were once nearly destroyed in our modern environment, where the use of chemicals such as dichlorodiphenyltrichloroethane – otherwise more easily known as DDT – kept these beasties at bay. DDT is a pesticide that is either very useful or very toxic, depending on who you ask or what journal study you read. Ultimately though, it was banned.

The Good And Bad Of DDT

DDT was used to keep mosquitoes under control, mostly because they spread malaria. It was used to keep lice numbers down too. So what happened when it was banned? As somewhat of a side effect of its use, DDT had kept bed bug numbers down. After it was banned, a bunch of other chemicals were used to treat bed bug infestations. The bed bugs, however, got smart and developed resistance to some of these chemicals. That resulted in a big UH OH for society as bed bug infestations are now on a major rise! Scientists from the University of Massachusetts Amherst and Korea’s Seoul National University decided that it would be important to find out more about resistant strains of bed bugs in New York. The work was published in the Journal of Entomology. Let’s see what they discovered, shall we?

When researchers got busy observing bed bugs in New York, they found these pests had mutations in their nerve cells. What does this mean? It means they are resistant to the chemicals used to kill them. Where the chemicals would previously have paralyzed and killed the bed bugs, the mutations mean that bed bugs are now outsmarting their opponents – us!

Let The Bed Bug Collecting Begin!

To get the scoop on bed bug resistance, researchers took a sample of easily controllable ones from Florida and compared these to ones from New York that were harder to deal with. So just how resistant were these little bugs?

Look at this partially engorged bed bug. It probably looks similar to the bed bugs in Milan after they feasted on my blood. Oh, and a fun fact of the day: the Italian word for bed bugs is cimice dei letti.

Researchers found that the bed bugs in New York had up to 264 times the resistance to the modern chemical used to kill bed bugs – deltamethrin. If we picture a nerve cell, it has these little sodium channels on the outer membrane bit. This is where the flurry of nerve impulses come to life. In the New York bed bugs, this nervous system mutation means they can keep feeding long after those Florida ones have been exterminated.

Grossaroo

When I was in grade 3, I made up the word ‘grossaroo’ to describe anything yucky. This word is fitting in the case of what happened to me recently when I was working at an agency in Milan. After a few nights at what seemed to be a nice corporate flat, I began to get loads of itchy, inflamed red bites. I awoke one night to find a flattened-looking bug moving across my otherwise clean, crisp white sheets.

I yelped and quickly squished it with my slipper, only to see it turn into a smattering of blood, which it just took from its recent feeding of my body! Just after, I saw another one. By morning, my bed looked like a crime scene with all those splats of blood and bugs. Eeek! Fortunately, I got moved to a new place and had everything washed. Hopefully, those Milan bed bugs weren’t too hard for the building owners to get rid of, unless they’re resistant beasts like those New York ones.

Bed Bug Warrior To The Rescue

So now you know (if you didn’t already!) that bed bugs do exist. Not only that, but they’re continually evolving to get smarter, doing so in ways that make it harder to get rid of them. For now, you can be smart by being extra cautious when traveling. Always check for signs of bed bugs around the mattress and furniture. Since not everyone shows bites from these little pests, prevention will remain the best line of defense. And while it’s not necessarily smart, it sure is fun when checking for bed bugs to yell “YOU’RE GOING DOWN!” If your parents ask what you’re doing, you can explain that you’re the self-appointed family warrior here to protect everyone from bed bugs.

Image credits: Unless otherwise specified, images courtesy of the National Pest Management Association.

The Recipe For A Perfectly Sticky Web May 31, 2009

Posted by Mrs Weird Scientist in Animals, Brain Power, Evolution, Insects, Tough Stuff.
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2 comments

Have you ever tried to bake a cake, only to find out that when it came out of the oven, it was dry and hard? Maybe you realized that you’d put in too much sugar. Or, maybe you cooked it for too long. Would you believe that spiders have a similar challenge when it comes to spinning their webs? Too much of a good thing can actually leave a web that’s far from perfect.

For this web to catch its prey, it needs to have just the right amount of stickiness and strength.  If all goes well for the spider, dinner will soon be served!

For this web to catch its prey, it needs to have just the right amount of stickiness and strength. If all goes well for the spider, dinner will soon be served!

For a spider to catch its prey, the web needs to be sticky but still remain strong. If the balance isn’t right, the web won’t catch a bug and it’ll be one hungry and grumpy spider!

A Killer Web Evolves

If you’re a spider, you’ve got your work cut out for you! To catch your prey, you want a web sticky enough that the bug gets caught inside but strong enough that the web doesn’t break from its struggles. With such a fine balance needed, spiders have evolved to get it just right.

Let the Construction Work Begin

To build those impressive webs we see, spiders start by putting down lines of dry silk. Then, they weave spirals of sticky silk to nab their prey. But, spiders of yesteryear didn’t build their webs in quite the same way.

Millions of years ago, spiders would lay down a coating of dry adhesive on these spirals. Rather than stick to the web, a bug would be entangled by these dry spirals. As a cool fact you can throw out at your friends, there are still some spiders today that weave their webs with this dry adhesive – we call them deinopoid spiders.

Yet things began to change, with orb weaving spiders evolving to make webs that were more effective at catching prey. Rather than continue to use this dry adhesive, spiders started to go the sticky route by using wet drops of a glue-like substance. When you think of glue, it seems that the sticker the glue, the better. Not for spiders though!

Curious Scientists Start Investigating

Some scientists started to wonder about these sticky webs – is stickier always better? To find out, Ingi Agnarsson of the University of Puerto Rico in San Juan and Todd Blackledge of the University of Akron in Ohio went on a mission to check out a lot of different spiders. They observed 17 species of orb weaving spiders. You’d have to like spiders quite a bit to watch so many different kinds! The full study results are in the Journal of Zoology.

It’s All About Force

The researchers tested the strength of the strands and the stickiness of them too. How’d they do that? Well, they stuck a piece of sandpaper in the web and then measured how much force was required to remove it.

To break a strand on the web, a specific amount of force is needed. When the researchers put the web to the test, they found that by using anywhere from 20% to 70% of this force needed to break the web, the sandpaper was released.

So, a stickier web might hold the insect but as it continues to struggle, the force would ultimately break strands of the web, causing the insect to be released. Yet, with the glue being a bit less sticky, the insect could pull away from a single strand, but it would get caught by the next one. Since the strands don’t break, they can continue to stick to the bug, making its fight a much harder one.

Spiders Are Impressive

It’s actually really impressive and cool when you think about the work that goes into creating a web with just the right balance of stickiness and strength. As for me, I’ll leave the bug-catching to those smart spiders. I think I’ll just stick to making cakes instead. Pun fully intended! Now if only there was a recipe for making good jokes…

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It’s Good To Look Like Poo February 22, 2008

Posted by Mrs Weird Scientist in Animals, Insects, Tough Stuff.
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Sometimes, it’s great to look like poo. That is, if you’re a caterpillar! Say hello to the Asian swallowtail caterpillar. It has some neat tricks up its sleeve to successfully stay camouflaged from predators. The first trick comes into play quite early on – when the caterpillar is black and white, with fine spines. Here, it resembles bird droppings. Later on, the caterpillars get older and grow larger, which means it’s a lot harder for the caterpillars to pass themselves off as bird poo. So, as the little critters fatten up, their color changes to a vivid green. Hmmm. Why might being green work well as a camouflage? If you guessed it’s because they can blend in with the leaves, you got it!

Caterpllar Camouflage

Credit: Ryo Futahashi. You can see the wee caterpillar on the left side of the picture looks a lot like bird droppings! On the right, the distinguished fellow is a grown caterpillar – the bright, green color really does make the caterpillar look like the surrounding leaves.

Manipulating The Caterpillar’s Camouflage

In an interesting twist of events, Ryo Futahashi and Haruhiko Fujiwara of the University of Tokyo in Japan, discovered a special way to keep the caterpillar looking like bird droppings. This means that the caterpillar still matures and develops, but it retains its poopy camouflage instead of growing into a green caterpillar that resembles leaves. How did the researchers accomplish this task? It’s not so easy.

Caterpllar Camouflage 2

It’s All About Genes

You might already be familiar with the concept of genes. Your genes are unique instructions that tell your body how to work. They control all sorts of stuff such as your hair or eye color. Humans aren’t the only ones with genes either! Caterpillar camouflage depends on genes. There are three genes that control the caterpillar’s camouflage. One is responsible for the green color, another for the black color and finally, one for those spikes we see on the very young caterpillars.

Tinkering With Genes

If researchers can find a way to meddle with these genes, they can change the caterpillar’s color. Hint hint. In the case of our Japanese scientists, they did their meddling with a hormone that rules the expression of all three genes. It’s called juvenile hormone. Researchers smeared a synthetic version of juvenile hormone on the back of a young caterpillar. Since the hormone controls the three genes that affect the caterpillar’s color, adding more of the hormone managed to keep the caterpillar looking poopy right through its development. It’s a cool manipulation because it teaches us more about how hormones and genes interact. As for all this talk about poo, I think my next blog post will be on something a bit more pleasant!

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