Interview with a Western Tent Caterpillar

Photo by Andrew Reding. Western tent caterpillars. 2014. CC. https://flic.kr/p/nwEuEP

(This post was inspired by my father, who saw tent caterpillars in July and told me I should write a blog post about them. Merry Christmas Dad!)

Me: What a lovely June day. The bees are buzzing, the flowers are blooming, the caterpillars are swarming. Wait, why are caterpillars swarming my Aspen tree? Get off of there!

Western Tent Caterpillars: Make me. I’m a native species, and I’m not doing anything wrong.

Me: You’re a gross creepy crawly mass of caterpillars, that’s what’s wrong.

W: Well we can’t all be hairless apes like you.

Me: And look at what you’re doing to this poor tree! You’ve eaten half of its leaves. How is it supposed to survive?

W: I wouldn’t worry about it. Trees are pretty good at bouncing back. Our population explosion will be over soon anyways. Maybe another four years or so.

Me: Four years? You mean I’ll have to stare at hundreds of wriggling caterpillars for another four years?

W: That’s what it looks like, yes. These explosions happen every decade or so.

Me: That is not very comforting. Why does your population explode anyway?

W: What can I say, sometimes the world needs more caterpillars. The cycles depend on weather, predators, pests and other factors. You guys haven’t cared to study us very much, so I’m not giving anything away.

Me: Will my poor aspen tree end up dead as a result of your munching?

W: It’s a pretty healthy specimen, so probably not. Healthy trees don’t usually die from infestation, it just make them weaker and more vulnerable to pests and drought.

Me: That’s not very comforting.

W: If it’s any consolation, the tree’s fighting back. It can make its leaves less nutritious next year, so fewer of us will survive. Anyways, getting rid of some leaves in the canopy actually helps the environment.

Me: Oh really? How’s that?

W: Fewer leaves means more light and rain reach the forest floor, giving saplings down there a chance to grow. I’ll also have you know that caterpillar poop is an awesome fertilizer.

Me: Eww, I didn’t really need to know that. How did you all get on my tree in the first place?

W: Mom put us here. Last August she laid a huge cluster of 300 eggs around a twig and covered us in this foam that hardened to look like grey Styrofoam. The finished clutch was as big as she was!

Me: Sounds pretty impressive.

W: It was! We started developing in our eggs, then took a long nap over the winter.

Me: What happened when you hatched? Why did you stick together?

W: We hatched just as the leaves started appearing in April. All of the larvae from that eggs sack decided to hang out because we are social butterflies. Okay, social moths.

Me: Why do they call you tent caterpillars?

W: Life as a soft and squishy caterpillar is not easy. Birds and rodents want to eat you, and parasitic wasps want to lay eggs in your insides. It’s very unpleasant. To avoid this, the colony builds a giant silken tent to hide under. If we aren’t feeding we’re in the tent. It’s shelter from the weather, protection from predators and a place to molt and grow.

Me: I’ve seen you stick your bodies out of the tent and twitch them. Is that a caterpillar dance party?

W: Nope, it’s a defense mechanism. We do it whenever a possible predator passes by. Hopefully they’re so confused they just keep walking and don’t try to eat us.

M: You said you turn into a moth, right? How long before that happens?

W: About 4-6 weeks after we hatch, everyone in the colony separates and finds their own spot to make a silken cocoon. We’ll pupate on anything from aspen leaves to house siding to lawn mowers.

M: I can’t wait.

W: Don’t worry, 10 days later we’ll emerge as beautiful light brown moths. Those moths flitting around your porch light are probably us. We usually mate within 24 hours of emerging.

M: Whoa, you don’t waste any time, do you?

W: Nope. Every female lays one egg clutch, and our whole life cycle takes about a year.

M: Yeah, but for most of it you’re stuck in an egg.

W: Touché.

M: So does this mean that my aspen tree will be infested by your children next year?

W: Probably. We are Canada’s national champion of eating leaves off aspen trees, after all.

M: I guess I’d better get used to you then.

W: Yep. You could spray pesticides on the tree, but that would kill the beneficial bugs too. It’s best just to let our predators or the weather finish us off.

M: Okay, I’ll leave you be… this time.

W: We appreciate it!

References

Click to access Tent-CaterpillarsDRAFT041113.pdf

http://www.nrcan.gc.ca/forests/fire-insects-disturbances/top-insects/13379
http://esrd.alberta.ca/lands-forests/forest-health/forest-pests/common-tree-insects-diseases/forest-tent-caterpillar.aspx
http://www.cityofgp.com/index.aspx?page=915
http://www.ctvnews.ca/canada/tent-caterpillar-outbreaks-plague-canadian-communities-1.1881540
http://www.cbc.ca/news/canada/edmonton/tent-caterpillars-defoliate-peace-country-1.1198924
http://www.countygp.ab.ca/EN/main/departments/agriculture/pest-disease-control/forest-tent-caterpillars.html
http://healthycanadians.gc.ca/healthy-living-vie-saine/environment-environnement/pesticides/tent-livreeamerique-eng.php

Click to access stelprdb5303047.pdf

Worried Woolly Bears

Photo by Tony Fischer. Wooly Bear Caterpiallar to Tiger Moth. CC. https://flic.kr/p/5DzVRB

While biking to school these days I’ve had to dodge the fuzzy black and orange caterpillars scurrying across the bike path. What are these critters, and why are they running so fast?

Child stars

Apparently woolly bears are the most recognizable caterpillar in North America, which is funny because I had never heard of them until this year. They’re much more famous than their adult form, the Isabella tiger moth, or Pyrrharctic isabella for you Latin fans. That’s probably because the moth is nocturnal and a dull yellow-tan. The fuzzy orange-and-black caterpillars are more noticeable, especially with their habit of crossing roads on sunny fall days.

The real reason for the woolly bear’s fame isn’t its cute black head or its orange and black fuzz. It’s because early North American settlers thought the native caterpillars could predict the winter weather. The wider the orange stripe, the milder the winter would be. They were basically a fall version of Groundhog Day.

This seems silly to us now, but in an era where your survival depended on how much food you stored up the fall, any information these settlers had about the winter would have been comforting.

Scientists aren’t really sure why some caterpillars have wider stripes than others. It could be climate, natural variety in the population, or something that changes as a caterpillar grows. Woolly bears may not predict the weather, but they are awesome for a lot of other reasons.

Autumn angst

Photo by D.Fletcher. Wooly Bear. CC. https://flic.kr/p/sjk7A

People usually see woolly bears in the fall when they’re in a hurry. They’re looking for somewhere to wait out the winter, and if they don’t rush, they’ll freeze. Well, they freeze anyway, but more on that later.

In the spring and summer woolly bears are solitary beasts. Native to southern Canada, they spend their days in meadows and fields hidden in patches of wildflowers. They’ll eat just about anything, from grass to maple leaves to dandelions.

But when winter rolls around they need to find logs, rocks, or tree bark to hide under, none of which are plentiful in wildflower meadows. So in the fall they wander out of their meadows and into more forested areas, which is why we see them crossing roads and bike paths. They’re just looking for somewhere cozy to wait out the winter.

Fuzzy popsicles

Over the winter woolly bears freeze solid. Starting with their heart. Think about how that would feel for a moment. Freezing is usually a supremely bad idea for a living thing. Water expands as it freezes, and prickly ice crystals damage cells and tissues. But woolly bears make a natural antifreeze called cryoprotectant, which keeps their bodies largely undamaged from freeze and thaw cycles.

If it warms up enough during the winter, the caterpillars might thaw and walk around a bit before refreezing again when it gets cold. However, just because they’re full of antifreeze doesn’t make them superheroes. Freezing and thawing multiple times over the winter increases their chances of death and organ damage. When it warms up in the spring, the caterpillars wake up and continue to eat before making a cocoon and transforming into a less-famous adult moth.

Why so hairy?

Woolly Bear fuzz close up. Photo by LadyDragonflyCC->;<. Woolly Bear close up. CC. https://flic.kr/p/7X2AYD/p/oBBdcR

Soft and squishy caterpillars are the ideal snack for birds, rodents, frogs and snakes. The woolly bear has a few ways to keep from becoming their next meal. First, they can run away pretty quickly. They will also curl up into a ball and play dead, keeping all their hairy bristles called setae on the outside. These setae do discourage some predators, but skunks and a few other animals have been known to roll them off before chowing down. It’s also thought that the hairs act as insulation during the caterpillar’s long winter’s nap.

Heal thyself

Besides being surrounded by predators, some woolly bear caterpillars get eaten alive from the inside out. Parasitic flies lay their eggs inside the caterpillar’s body. After they hatch, the larvae munches on the woolly bear’s insides before exploding out of its side. Ick. A 2009 study at the University of Arizona found that woolly bears self-medicate on certain plants which cure the parasite. Caterpillars infected with parasites ate way more alkaloids than their non-infected peers. However, too many alkaloids are poisonous, so woolly bears have to balance poisoning themselves with getting eaten alive by fly babies. Not a fun choice.

So watch out for these speed demons on a road near you this fall, and please try not to squish them.

References

https://bioweb.uwlax.edu/bio210/s2013/clinton_kevi/adaptation.htm
https://www4.uwm.edu/fieldstation/naturalhistory/bugoftheweek/woolly_bear.cfm
http://blogs.scientificamerican.com/budding-scientist/httpblogsscientificamericancombudding-scientist20110713adopting-a-caterpillar-and-other-adventures/
http://newt.phys.unsw.edu.au/~jw/cryoblurb.html
http://www.britannica.com/animal/woolly-bear
http://lancaster.unl.edu/feature/guess10_3.htm
http://web.extension.illinois.edu/dmp/palette/061015.html
http://news.nationalgeographic.com/news/2009/03/090313-self-medicating-caterpillars.html
https://bioweb.uwlax.edu/bio210/s2013/clinton_kevi/classification.htm
http://escarpmentfund.ca/blog/how-fuzzy-was-he/
http://eol.org/pages/863046/details
http://bugguide.net/node/view/539
http://pnwmoths.biol.wwu.edu/browse/family-erebidae/subfamily-arctiinae/tribe-arctiini/pyrrharctia/pyrrharctia-isabella/
http://www.silkmoths.bizland.com/spisabel.htm
http://extension.psu.edu/franklin/news/2012/wooly-bear-caterpillars-2013-purported-peerless-prognosticators

8 things I didn’t know about native bees

Bees come in a rainbow of colours. Check out this shiny green sweat bee. Photo by Jim McCulloch, CC. Sweat bee on coral vine flower. https://www.flickr.com/photos/jim_mcculloch/2950920481/

I have a confession to make; I’m an insect geek.

And when it comes to social insects like bees and ants I’m even geekier than usual.

So when I learned that the Learning Garden at the University of Ottawa was holding a free workshop on insect identification, I jumped at the chance to learn more.

One of the coolest things we learned was how to tell the difference between flies and bees. You would think this would be easy, right? Bees are fuzzy with yellow and black stripes. Flies are black and shiny.

In fact, it isn’t that simple! Many of the native bee species in Canada look like tiny flies. Also, many fly species are camouflaged to look like bees so predators won’t mess with them. So how do you tell them apart? Well, look at the antennae. In most cases, flies have short, stubby antennae and bees have long, languorous ones.

Armed with this information, we stepped out into the University’s learning garden to find some insects. Now that I knew what I was looking for, I was amazed to see how many bees there were! They came in all shapes and sizes, from 2mm to 2cm. They also came in an exciting palette of colours, from black to grey to bright green! Even cooler, all these bees were native to Canada!

I first learned about native bees while writing an essay on the possible causes of the major honey bee deaths in North America. I learned that these unsung-heros do a great job of pollinating farmers crops for free! It’s sad that we aren’t taught more about them in school. So I did some reading, and here’s what I found out.

1. Everything you’ve been told about bees is a lie

Okay, that’s a bit of an exaggeration. It’s more like ‘everything you’ve been told about bees only applies to honey bees’.

Out of 19,000 bee species worldwide, most museums, science centres, schools and documentaries only talk about one: the European Honey bee. You know, the queen with thousands of female workers, the yellow and black-striped workers bringing back nectar and pollen to feed the larvae, the waggle dance to communicate where flowers are located. You’ve heard it all before.

And there’s a good reason to talk about them. European honey bees are commercially valuable. They were domesticated a long time ago to produce honey and pollinate crops. Without pollination, we wouldn’t have fruits like apples, tomatoes, cherries, pumpkins, strawberries or blueberries. In fact, we need pollinators for 1 out of every 3 mouthfuls of food we eat!

The European honeybee is so essential to agriculture that European settlers brought them to Canada. The European Honey bee is now a mainstay of the Canadian economy. However, there were bees in Canada already, around 730 species to be exact! And even though we don’t talk about them very much, they’re still here! For some crops, like blueberries, native bees are even better pollinators than honey bees.

2. They came from underground

Bees weren’t always cute and cuddly pollen-eaters. They used to eat meat! Yep, bees evolved from predatory digger wasps, which still exist today.

Why this drastic change from munching on other insects to sipping nectar? Well, it had everything to do with the arrival of flowering plants. Believe it or not, flowers didn’t exist until the Cretaceous period (1465-65 million years ago). This means that dinosaurs pre-date flowers. Can you imagine a world without flowers? Weird, huh? The evolution of flowers created a whole new food source, and bees, wasps, butterflies and moths evolved to eat it up. Maybe sipping nectar was easier than catching live prey!

3. All by myself…

Considering that honey bees are the poster child of the social insect, I was surprised to learn that most native bees in North America not social at all. They live by themselves, and are called solitary bees. Each female builds her own nest, lays her own eggs, and collects all her own pollen and nectar. Who needs hundreds of sisters when you can be independent?

What does a solitary bee’s life cycle look like? A female finds a male to mate with, then digs or finds a burrow to lay eggs in. She collects a huge ball of nectar and pollen, then lays an egg on top of it. When the egg hatches, the larvae feeds on the pollen, and in the fall becomes an adult. The adults hibernate through the winter to emerge in the spring.

4. Hives? No thanks.

Bee exiting a burrow. Photo by Rob Cruikshank, CC https://www.flickr.com/photos/84221353@N00/5713786629/

Most solitary bees don’t live in fancy hives, but in holes in the ground. Yep, kind of like hobbits. 90% of native bee species lay their eggs in burrows in the ground.

Osima bees have by far the cutest homes. They like to nest in tiny spaces including snail shells, keyholes and even locks!

5. Busy bee? No, lazy bee.

Some bee species trick someone else into doing all the work for them. They lay their eggs in the nests of other bees, and avoid the work of collecting pollen and making a nest. This behaviour is called cleptoparastisitm. So much for busy bees!

6. Bumbling around

The fuzzy Bumble bee is indigenous to Canada. It’s the only bee that sticks around to feed its growing larvae. All other native bees hightail it out of there once the eggs are laid. In the wild, bumble bees also nest in the ground, but usually let someone else do the work. Holes in trees or abandoned rodent dens make a cozy nest. However, domesticated honey bees are managed using hives.

7. Picky, picky

Some Canadian bees are picky eaters. They only collect nectar and pollen from one kind of flower. They aren’t doing this to be difficult. They’re doing it because they have evolved to be perfectly suited to that flower. For example, the bee Melissodes desponsa only visits thistles. Ecologists call picky eaters ‘specialists’. Most Canadian bees are ‘generalists’ which means they can get food from many different kinds of flowers.

8. The extinction factor

Because of their sensitivity to environmental factors, some bee species are prone to extinction. This is especially true for specialists that only feed on one type of flower. If the flower disappears, they are in trouble. And it’s not just climate change that is causing their food to disappear. Many of the flowers we grow in our gardens come from Europe, and most native bees can’t use them for food.In addition, chemical pesticides meant for pesky insect will also kill bees.

Okay, enough doom and gloom. What can you do to help native bees? You can give them food by planting native wildflowers, or by waiting to mow those pesky ‘weeds’ until after they have flowered. You can give them places to live, by leaving bare patches of ground in your garden. You can even install woodblocks with holes drilled into them. These are called trap-nests, and will attract bees that like to live in pre-existing holes.

References
http://sci.waikato.ac.nz/evolution/plantEvolution.shtml
http://www.pollinationcanada.ca/index.php?k=358
http://www.biology.ualberta.ca/bsc/ejournal/pgs_03/pgs_03_main.html

Click to access Recommendations%20for%20Conservation%20of%20Pollinators%20on%20FarmlandFinal_DSC.pdf

http://www.gnb.ca/0171/10/0171100025-e.asp

Confessions of a Fly Sex Researcher

Fruit flies getting it on. Taken from http://www.nature.com/nature/journal/v489/n7414/images/489038a-f1.2.jpg

You’re a third year biology student confused about what on earth you’re going to do once the diploma is in hand. Where will you work? What will you specialize in? Do you have what it takes to do a masters, as your chances of getting work with just a bachelors degree is slim to none?

Your solution? Do an 8 month honours project.

If you’re particularly gung-ho, do two at the same time. (Actually, don’t. It wasn’t one of my better life choices. More on this later).

Once you’ve decided that you’re going to dedicate 8 months of your life to a certain topic, you have to decide what that topic is going to be. For me, this was relatively easy. I liked insects. I liked evolution. So I signed up with a professor who did too. He used fruit flies to study various evolutionary theories. Piece of cake!

After reading many journal articles to make sure our brilliant study had not already been done by someone else (this is an occupational hazard in research), we decided on an experiment.

I would find out what female fruit flies found sexy about the males.

A male Drosophila psuedoobscura flaunting a transparent abdomen complete with orange testes. Photo credit Alex Wild. http://blogs.scientificamerican.com/compound-eye/2013/07/03/drosophila-pseudoobscura-a-model-fruit-fly-for-the-real-world/

We suspected it had something to do with the male’s orange testicles. Because, seriously, why else would you have a transparent abdomen and bright orange testes if not to impress the ladies?

As you can imagine, fly sex is a great topic at dinner parties. I am usually asked the following questions:

Q: There are fruit flies everywhere in my kitchen! Can I donate them to you?

A: I understand your pain, but my lab does not take fly donations. I was looking at a very specific species, Drosophila pseudoobscura, which lives in western North America. The flies I worked with originally came from Arizona, but had been bred in labs for many generations to get as uniform a population as possible.

Q: Do all flies have orange testicles?

A: No. I haven’t studied the behinds of other flies, so I can’t say for sure if there are other species out there with florescent testes. There may be, who knows?

Q: Can you see fly testes?

A: Well, the flies are tiny (5mm), so their testes are miniscule. You can see them with the naked eye, but to study them I took pictures using a dissecting microscope.

Q: How to you make flies stand still for pictures?

A: I asked them nicely. Just kidding. I gassed them with carbon dioxide, which knocks them out for a few minutes.

Q: Did you watch fruit flies having sex?

A: (Sigh). Of course I did. To find out which males the females found most attractive, we put two virgin males in an arena with a virgin female. The male she chose to have sex with was the one she liked best. Believe me, the novelty of watching fly sex wears off after the 10th coupling.

Q: Wait a minute, why did you use virgin flies?

A: We had to make sure all our flies had the same level of sexual experience. Like humans, flies can learn from past experiences, which subsequently affect they find attractive in a mate. We wanted our females to have a clean slate.

Here is a lovely life cycle from a pest control company. I guess that it’s important in their line of work! http://www.orkin.com/flies/fruit-fly/life-span-of-fruit-fly/

Q: How do you know for sure that your flies are virgins?

A: Fruit flies have a lifecycle similar to butterflies. In D. pseudoobscura, the adult flies can’t reproduce until 48 hours after they struggle out of their pupa (Snook & Markow, 2001).When my flies started emerging from their pupae, I segregated them by sex every 24 hours to make sure they couldn’t get up to any funny business. Sorting hundreds of flies is not an exciting way to spend your Saturday, and thankfully I only had a few Saturdays like that.

Q: What did you find out? Do females find orange testes sexy?

A: Unfortunately, they do not. The size and colour of a male’s testes had nothing to do with whether or not a female chose him. We found the females were more interested in the male’s pheromones, and were selecting mates based on that.

Q: Then why do the males have orange testes?

A: I have no clue. But it’s not related to sex. If you find out, let me know.

Q: Is your research applicable to humans?

A: Not in the slightest! It’s true that flies and humans share many genes, and flies are used as model organisms in studies that can apply to humans. However, human courtship and fly courtship are worlds apart. In fact, different fly species have different kinds of courtship. Therefore, my research can only be applied to this species of fly. Unless, of course, you know any humans with orange testes…

Note: Alex Wild has some more beautiful pictures of some pseudos on the Scientific American blog. Apparently they are an under-photographed species. Go check them out, and remember to look for the orange!

http://blogs.scientificamerican.com/compound-eye/2013/07/03/drosophila-pseudoobscura-a-model-fruit-fly-for-the-real-world/

Snook, R. R., & Markow, T. A. (2001). Mating system evolution in sperm-heteromorphic Drosophila. Journal of Insect Physiology, 47(9), 957-964.