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Soil Sidekicks – Trapdoor Spider

July 30, 2015

The way our next Soil Sidekick hunts may seem like something out of a horror movie, but don’t worry – unless you are a pint-sized arthropod, you have nothing to fear from the trapdoor spider.

The elusive trapdoor spider measures in at a little over 1” in length. These smaller relatives of the tarantula are black or brown with a glossy exterior. Like other arachnids, they have eight legs and two body segments. They have relatively long lifespans, and can live up to 20 years.

Cork-lid trapdoor spider (Ctenizidae: Ummidia). Photo courtesy of Greg Gilbert from Dahlonega Area, Georgia, USA, via Wikimedia Commons.

Cork-lid trapdoor spider (Ctenizidae: Ummidia). Photo courtesy of Greg Gilbert from Dahlonega Area, Georgia, USA, via Wikimedia Commons.

Like the tarantula, the trapdoor spider is a mygalomorph, a member of a smaller group of spiders characterized by downwards-oriented fangs. Trapdoor spiders can be found all over the world, including species in the genus Ummidia and one known species in the genus Cyclocosmia in North Carolina. Although they are elusive, trapdoor spiders are considered common and can be found in your own backyard. Due to their elusive nature, these masters of camouflage are not well studied in this area.

The trapdoor spider is venomous like most spiders, but its venom is comparable to a wasp sting, causing only minor pain and swelling. These arachnids are not aggressive and will only bite people in self-defense. If you find one in your home, it’s best to capture it in a container such as a jar and release it outdoors.

Spiders have many interesting adaptations for survival in a world that is often harsh to such small creatures. Arachnids and their other cousins in the subphylum Chelicerata, including horseshoe crabs and sea spiders, possess specialized jaws called ‘chelicerae’. In trapdoor spiders, these mouthparts are modified with a row of hardened digging spines on each chelicera called a ‘rastellum’. These tiny projections resemble teeth or hairs, and are designed to help move the soil as the spider constructs its underground burrow.

Cork-lid Trapdoor spider burrow saved intact in baking powder tin ca late 19th century. Photo courtesy of Jon Richfield, via Wikimedia Commons.

Cork-lid Trapdoor spider burrow saved intact in baking powder tin ca. late 19th century. Photo courtesy of Jon Richfield, via Wikimedia Commons.

Although they may resemble a fifth pair of legs, enlarged mouthparts called ‘pedipalps’ are specialized in all spiders, like the chelicerae. These parts are used for shaping their web silk and assisting them in feeding, but also for reproduction in males.

Trapdoor spiders are named after the special burrows that they construct. They create their homes by digging down into the soil, lining them with silk that keeps in moisture and provides a surface on which the spiders can more easily walk around. The ‘trapdoor’ entrance is created using a blend of silk, soil, and other materials such as moss or leaves found around the burrow. This recipe makes a door that blends in with the environment, camouflaging the spider’s home. It is hinged with stretchy silk, and its underside has holes so that the spider can grip with its legs or fangs and spring out at just the right moment. This also allows the occupant to hold the door tightly closed if a predator attempts to enter the burrow.

Trapdoor spiders lay silk ‘tripwires’ around the entrance of their dens, then lie in wait for unsuspecting prey to come along and accidentally touch the silk. They can feel the vibrations along the silk, judging the size and distance of their (typically arthropod) prey based on what they sense. Once the spider senses that there is a meal waiting outside, it springs open the door, grabs its prey, and retreats once again into the burrow.

Cyclocosmia sp. in burrow, from Appalachia. Photo courtesy of Marshal Hedin, via Wikimedia Commons

Cyclocosmia sp. in burrow, from Appalachia. Photo courtesy of Marshal Hedin, via Wikimedia Commons.

Ravine trapdoor spiders (Cyclocosmia truncata) have an interesting body shape. Unlike other trapdoor spiders, their abdomens are cut short to form a hard, patterned disc-like shape that serves as a stopper for their burrows. They use the width of their abdomens to seal themselves safely inside their dens, using their hardened backsides as a protective shield.

Certain species of native mud dauber wasps prey on any spider they can catch, including trapdoor spiders. A female wasp will paralyze the arachnid, bringing it back to the mud nest and laying her eggs in it while it is still alive so that her larvae have a fresh source of food when they hatch. The trapdoor spider’s other natural enemies may include mice or other spiders.

Although they can live longer, males often only live about nine months past maturity due to the fact that they leave their burrows and wander the landscape to find a mate in the springtime, placing them in much more danger than females.

Do female trapdoor spiders really eat males? That depends – sometimes a female spider will mistake a male for prey at her front door, so he must approach cautiously. Male trapdoor spiders have a special tooth-like hook on their first pair of legs used for hooking the female’s fangs to hold them back as he enters the burrow. If the female is not receptive to his advances, she could still decide to kill him, and he might become her next meal – however, this is not as common as you may think.

Although these interesting arachnids may be widespread, they are not often seen. Consider yourself lucky if you have the chance to see a trapdoor spider springing into action.

Soil Sidekicks is an inside scoop starring animals that live in and around the soil. Did you know that there are more living creatures in a shovelful of rich soil than there are people on the planet? Get the dirt on where the Sidekicks live and discover more about the soil that sustains us at Dig It! The Secrets of Soil.

Claire Carrington is a Museum Public Relations intern, and currently a senior at Campbell University.

Thanks to Dr. Colin Brammer, Coordinator of the Natural World Investigate Lab for information and guidance.

First photo: By Greg Gilbert from Dahlonega Area, Georgia, USA (Cork-lid trapdoor spider (Ctenizidae: Ummidia))
{CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)}, via Wikimedia Commons

Second photo: By Marshal Hedin (http://www.bio.sdsu.edu/pub/spiders/App/index.html)
{CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)}, via Wikimedia Commons

Third photo: By Jon Richfield (Own work)
{CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)}, via Wikimedia Commons

Nocturnal Insects (What Time is it in Nature)

July 25, 2015

It’s National Moth Week! To celebrate, we hosted our fourth annual Moths at Night program at Prairie Ridge last weekend. During the event, a few Museum staff did presentations about moths and the other arthropods we find at night, but the bulk of the event centered around moth observation and appreciation. We set up several blacklight stations and a mercury vapor light station and participants moved from station to station looking for moths and other insects. Many participants photographed the moths they saw so they can submit them our Natural North Carolina citizen science project as well.

Let’s explore some moths and other insects that you can find at Prairie Ridge! Many of these will only be visible at evening programs, but you can spot some of them during the day if you’re lucky.

A lot of the moths we get at Prairie Ridge aren’t what you would call “showy” moths.  This leafroller moth is a great example of the standard small, brown moths that you’ll find anywhere you look for moths:

Leafroller moth

Photo by Chris Goforth

That’s Argyrotaenia velutinana, also known as the Red-banded Leafroller, a member of the Tortricidae family of moths.  There is very little information available about them, such as what their host plants are, how they develop, etc, so there’s not a lot to learn about this particular moth yet.  There is generally a lot of work still needed on what many entomologists affectionately call “LBMs,” or little brown moths.  Someday we may know more about this LBM!

We get dozens of small moth species at blacklights at Prairie Ridge.  This moth was a little more distinctive and showy compared to the Red-banded Leafroller above:

Grass Veneer

Photo by Chris Goforth

This moth belongs to the grass-veneer genus, a genus made up of small moths that feed on grasses as caterpillars.  Given the amount of grass we have at Prairie Ridge, it’s no wonder that we see a lot of grass-veneers!  This moth is a Double-banded Grass-veneer, or Crambus agitatellus.  You can find adults of this species from about June through August throughout most of its range across the eastern 2/3rds of the US.

Some moths have excellent camouflage.  This moth looks like bird droppings:

Bird Dropping Moth

Photo by Chris Goforth

The Exposed Bird Dropping Moth, Tarache aprica, is well protected from predation as few animals want to eat something that looks like bird poop.  You’ll find the caterpillars of this moth feeding on hollyhocks and can occasionally flush an adult from a hiding place during the day.   They’re found throughout most of the eastern US except the northern Midwest.

One exciting find at our blacklights this year was a satiny white visitor:

Snowy Urola

Photo by Chris Goforth

Snowy Urolas (Urola nivalis) are thought to be a grass feeding species as caterpillars and are found throughout the eastern US, though they are a common sight in the southeast.  This species has a shiny white appearance with a small dark spot in the center of its back.  They fly throughout the summer and may have two generations a year.

One of our most showy moths at our National Moth Week celebration the last four years has been the Rosy Maple Moth:

Rosy Maple Moth

Photo by Chris Goforth

These large, brightly colored moths go against the generality that butterflies are colorful while moths are not.  Rosy Maple Moths feed on a variety of trees as caterpillars, including their namesake maples, but do not feed at all as adults.  These gorgeous, bright members of the silk moth family are found throughout the eastern US and can be spotted at lights at night from late spring into early fall in the south.

We saw a lot of moths, but you never get just moths coming to blacklights.  Some other visitors to the lights included caddisflies:

Leptoceridae

Photo by Greg Bryant

and scarab beetles:

Grapevine beetle

Photo by Greg Bryant

When you have a lot of insects coming to lights, you often attract non-insect predators looking to score an easy meal too.  A few of our citizen scientists spotted this lovely toad wandering around near one of the light rigs:

Toad

Photo by Greg Bryant

There were so many insects flying around the area that I suspect that this was a very happy, well-fed toad!

National Moth Week ends Sunday, but I encourage you to explore moths and other nighttime insects throughout the year.  By simply turning on your porchlight and looking to see what comes to the light, you can learn a lot about the hidden nighttime world around you.  We hope you’ll also consider attending an upcoming evening program at Prairie Ridge so that you can see some of the great moths featured here and other amazing nighttime animals!

What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Museum’s public outdoor facility, Prairie Ridge EcostationFind out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!

Soil Sidekicks – American Woodcock (Timberdoodle)

July 21, 2015

One of our Soil Sidekicks is particularly good at hiding. So good, in fact, that it can be almost impossible to spot one huddling in the grasses of a field at the forest’s edge.

Meet the AmericAmerican Woodcock (Scolopax minor)an woodcock (Scolopax minor), also known as the timberdoodle. This plump little bird’s beautiful gray, black and brown feathers serve as the perfect camouflage in its natural habitat of brush near the edge of the woods. The American woodcock’s chest and side feathers are characterized by a rich range of colors from yellowish-white to deep tan, and its legs are short and brown or gray.

This little scout has large, wide-set black eyes used for scanning the skies for predators. It has one of the largest sight ranges of any bird, and can see 360 degrees around its head – even behind it. The woodcock is usually solitary, and it is crepuscular, meaning it is most active at dawn and dusk in order to avoid predators.

American Woodcock (Scolopax minor)

American Woodcock (Scolopax minor)

One of the most noticeable features of the woodcock is its long, straight bill used for probing in the soil for prey. These inquisitive birds primarily feed on earthworms, which make up more than 90 percent of their diet, so they spend a lot of time searching in and around soft soils for their favorite foods. Their unique bills are prehensile, meaning that unlike most birds, the woodcock can flex the upper half of its bill (mandible) while using it to investigate the ground. This motion resembles a “yawn” and helps woodcocks hunt slippery earthworms in the soil, since the birds cannot fully open their long bills while they are probing underground. The tip of the bird’s bill also has nerves to help it locate worms crawling around in the earth. One study suggests that these earth detectives are even capable of ‘tasting’ the soil in order to find their favorite meals.

When searching for food, woodcocks will often walk with a funny ‘bob’ that resembles a dance. It is thought that this motion of rocking the body back and forth while stepping heavily with the front foot causes worms to move around in the soil, making them more easily detectable. This funny dance-like movement is also part of the male’s courtship display.

Specialized flight feathers on an American Woodcock specimen

Specialized flight feathers on American Woodcock specimens

The male woodcock’s famous courtship show begins with a distinct “peenk” call around dawn or dusk. After “peenking” and doing his dance, he will take off into the air to fly around while singing a song to attract a mate. While descending in an elaborate zig-zag pattern, the bachelor bird creates a twittering sound as air whistles through his highly modified outer flight feathers on his wings. When he lands, the male will “dance” for any females (hens) who have flown in to watch his display.

After mating, the hen will make a shallow nest on the ground in leaf litter, where she typically lays four eggs. When a predator approaches the nest, she will lie perfectly still, hoping that her excellent camouflage will keep her out of sight. If that doesn’t work, she will put on a show much like the woodcock’s cousin, the killdeer – the hen will flush from the nest and pretend to be injured in order to draw the danger away. Although male woodcocks put on quite a show for hens, they do not assist in defending the nest or raising the chicks – indeed, they continue to dance and display to attract other females.

When the chicks hatch, they are precocial, meaning that they are ready to leave the nest within just a few hours of emerging from the egg. At around two weeks of age, they are capable of flying short distances and look like adults. Young woodcocks will follow their mothers closely for about five weeks, learning to hunt for worms and survive on their own until they are fully grown and become independent.

American Woodcock specimen

American Woodcock specimen

Their closest relatives are shorebirds such as sandpipers and snipes, but woodcocks are found closer inland near wet thickets, brushy swamps, and agricultural areas. They can be found as far north as Canada during warmer months and as far south as Florida during the winter. These birds are present all across North Carolina year-round, but primarily live in the Coastal Plain and the Piedmont. They are sensitive to the cold, so populations migrate south as the weather turns chillier. However, as the weather warms again, their northward migration signals springtime in many areas of the Eastern United States.

Each February, the Wake Audubon Society hosts the annual Woodcock Watch to scout out this Soil Sidekick – watch their webpage for more information. If you hang around the edge of the woods at dusk or dawn this summer, you may be lucky enough to see this little bird dancing.

Soil Sidekicks is an inside scoop starring animals that live in and around the soil. Did you know that there are more living creatures in a shovelful of rich soil than there are people on the planet? Get the dirt on where the Sidekicks live and discover more about the soil that sustains us at Dig It! The Secrets of Soil.

Claire Carrington is a Museum Public Relations intern, and currently a senior at Campbell University.

Thanks to John Gerwin, Research Curator of Ornithology and John Connors, Former Coordinator of the Naturalist Center for information and guidance.

National Moth Week – Coming Soon!

July 16, 2015

The fourth annual National Moth Week takes place July 18-26, and we’re ready to help you celebrate! Our National Moth Week event, Moths at Night, will take place at Prairie Ridge Ecostation this Saturday, July 18 from 8pm-midnight. The Museum has participated in National Moth Week since the very beginning, and we’re excited to bring this fun and engaging citizen science-focused event back again this year.

For those of you who are thinking, “Why do moths deserve a whole week?” let’s cover some moth basics. Moths are an incredibly diverse group of organisms, with tens of thousands of described species. Some estimates suggest that there may be as many as half a million species total on our planet. Moth enthusiasts worldwide do comprehensive surveys of the moths visiting their backyards and it is not uncommon for a single yard to host hundreds of species. One moth researcher in western North Carolina, for example, has discovered over a thousand species of moths – just in his backyard! Moths have an amazing diversity that is well worth exploring.

The sheer number of species alone makes moths worthy of celebration, but those many, many moth species also fulfill essential roles in our environment. Some moths are pollinators of night-blooming flowers, while other moths pollinate flowers during the day. A lot of our day-flying moths are colorful and showy like butterflies, such as this Ailanthus Webworm Moth:

Ailanthus webworm moth

Ailanthus Webworm Moth. Photo by Chris Goforth.

Moths are also great indicators of ecosystem health, a sort of canary in a coal mine if you will. Many species are tightly linked to a specific ecosystem. If the moths disappear, it tells scientists that there’s something wrong in that habitat worthy of further study. If a problem is found, changes in land management may help alleviate the environmental problem.

Perhaps most importantly, moths are a very valuable food source for a wide variety of animals. Like birds? Then you should like moths! Many species of birds depend on moths as food, though many rodents, reptiles and amphibians, and even fish are known to feed on moths as well.

Moths can be found in an astonishing variety of habitat types. Some moths are highly specialized, such as the classic ecological example of the yucca moth and yucca. Certain species of yuccas depend entirely on a single species of moth for pollination such that the two are always found together and elimination of either the moth or the yucca from the environment results in the loss of both species. Some moths are known to live inside the upper regions of carnivorous pitcher plants (a risky place to live if you’re an insect!) and others are aquatic for most of their lives and live on land only as adults. Moths live almost everywhere on our planet but the ocean!

Moths are generally harmless to humans, but some moths contain toxins that make them unpalatable to a variety of would-be predators and there are some blood-sucking moth species known from southern Europe and Siberia. However, moths can harm us indirectly. Some moth caterpillars are pests and compete with us for food (such as corn) and fiber (such as cotton). Other moth species, such as the Fall Cankerworm, are known as forest pests that can damage timber yields and still other moths destroy our clothing. While many moths perform important services that we benefit from, some species are capable of inflicting massive damage on natural products we use

Apart from all of these reason why moths are important and worthy of study, they are also quite beautiful. During last year’s Moths and Night celebration, we documented several beautiful moths, including these:

Skiff moth

Skiff Moth. Photo by Chris Goforth.

Beautiful wood nymph moth

Beautiful Wood Nymph Moth. This moth is a bird dropping mimic! Photo by Chris Goforth.

Banded tiger moth

Banded tiger moth. Photo by Chris Goforth.

Black bordered lemon moth

Black bordered lemon moth. Photo by Chris Goforth.

This amazing moth is what Woolly Bears turn into!:

Isabella tiger moth

Isabella tiger moth. Photo by Chris Goforth.

The showiest visitor the last two years has been the Tuliptree Silkmoth:

Tulip tree silk moth

Tulip tree silk moth. Photo by Chris Goforth.

Other gorgeous moths include the Rosy Maple Moth (I like to call it the “rainbow sherbet moth”), the Tuliptree Beauty moth, and the tiny but spectacular Sparganothis Fruitworm Moth. Sure, not all moths are showy, but many of them will surprise you.

If you’d like to learn more about moths or National Moth Week, please consider attending our Moths at Night program on Saturday, July 18! We’ll have several moth-attracting light stations set up on the Prairie Ridge grounds where you will be able to see a wide variety of moths and other nocturnal insects. We’ll have experts on hand to help you identify some of our common moths and we’ll send you home with a guide to help you explore the moths living in your backyard. Bill Reynolds, head of the Museum’s Arthropod Zoo will introduce you to the wide world of moths at the beginning of the event.  We also want to document the moths that come to our lights so that scientists can use our data in their studies. If you have a camera and are willing to take some photos, we’ll have a few stations set up where you can upload photos to this year’s featured citizen science project, Natural North Carolina.

Even if you can’t make it to Prairie Ridge, we hope you’ll participate in National Moth Week anyway! Just flip on your porch light one or more evenings between July 18 and July 26, snap a few photos of the moths you see, and submit them to Natural North Carolina. You don’t even have to identify your moths to help. Simply uploading a few photos to Natural North Carolina is enough to help scientists worldwide learn more about these amazing nocturnal insects. We’ll share some of our favorite submissions by NC citizen scientists on our Google+ page throughout the week so everyone can see some of the amazing moths that call North Carolina home – we have some great ones.

Join us and celebrate moths during National Moth Week!

For more information about Moths at Night, please visit the listing on our Programs and Event page.

Mountain Mint Pollinators (What Time is it in Nature)

July 11, 2015

Last week’s What Time is it in Nature discussed Mountain Mint, a plant that you can find in Prairie Ridge’s Nature Neighborhood Garden.  This week, let’s explore some of the amazing diversity of pollinators that make use of nectar while the plant is in bloom!

When many people think of pollinators, they automatically think of butterflies.  Butterflies make up a part of the pollinators you’ll see on Mountain Mint, including Common Buckeyes, Gray Hairstreaks, and Red-banded Hairstreaks.  This Juniper Hairstreak is a less commonly observed butterfly on our Mountain Mint, but is quite beautiful:

Juniper Hairstreak butterfly

Photo by Chris Goforth

It’s not quite as obvious from this photo as it might be, but the hairstreaks get their name from a thin, fragile tail that protrudes off each of their hind wings.  They tend to have the sort of general body shape of this butterfly as well, though the color patterns vary considerably from species to species.

While many people think first of butterflies when they hear the word “pollinator,” other people will think of bees.  Honey Bees are not native to the US and were imported from Europe soon after Europeans started colonizing North America, but you’ll find them on many of our native plants, including Mountain Mint.  However, these bees are much more commonly spotted on the plant in our garden:

bumble bee

Photo by Chris Goforth

Bumble bees are large bees that form small colonies underground.  You will see them flying from flower to flower, gathering nectar and pollen similarly to Honey Bees, though many species are quite a bit larger than the average Honey Bee.  Bumble bees are important pollinators for many native plants and are the focus of several native pollinator conservation efforts and citizen science projects.

Bees are often seen on flowers, but their wasp relatives can be even more abundant on Mountain Mint.  Take this spider-hunting wasp:

spider hunting wasp

Photo by Chris Goforth

Spider-hunting wasps get their name from a behavior they exhibit during reproduction.  A female wasp will sting a spider to paralyze it, bury it, and lay one or more eggs on the spider.  When the eggs hatch, the wasp larvae have fresh meat to eat as they grow.  This may seem gruesome, but it’s an important part of nature that helps keep spider populations in check.  And, while the larvae may be carnivorous, the adults are not.  They feed primarily on nectar, and you will see many of them sipping nectar from the tiny flowers on the Mountain Mint.

This wasp has similar reproductive requirements:

Scoliid wasp

Photo by Chris Goforth

Scoliid wasps are also considered parasites because they paralyze prey for their larvae to feed on after hatching.  However, scoliid wasp larvae feed on the larvae of scarab beetles rather then spiders.  Adult females will dig into the ground to find a beetle grub before stinging it and laying her eggs.  Like the spider-hunting wasps, the adults feed primarily on nectar and you can see them feeding on nearly any flowering plant at Prairie Ridge in the summer, including Mountain Mint.

Butterflies, bees, and wasps are all commonly spotted pollinators, but let’s not forget some of the other groups of insects!  This gorgeous fly can sometimes be found feeding at the flowers of Mountain Mint:

Tachinid fly

Photo by Chris Goforth

Tachinid flies are parasites like the spider-hunting wasps and scoliid wasps, though their specific host species varies by the fly species.  The adults often feed on nectar and help spread pollen around for a variety of plants.

The Mountain Mint is positively abuzz recently as the flowers bloom and produce nectar.  Be sure to visit the Nature Neighborhood Garden on your next visit to Prairie Ridge.  One quick look is all it takes to spot a dozen or more species of butterflies, bees, wasps, flies, and beetles – well worth a trip out to see it!

What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Museum’s public outdoor facility, Prairie Ridge EcostationFind out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!

(Photos by Chris Goforth)

The hole truth about animals that bore

July 10, 2015
Featured Image -- 1733

Originally posted on Research & Collections:

Summer is here, it’s hot, the kids are out of school, and by now I expect they’re pretty bored. Perhaps it’s time to go outside and see how bored other things are. For instance, if you’re at the beach, you might find a clam shell with a perfectly circular hole in it. That’s a bored clam shell. Or maybe you’re lucky enough to find a rock or coral with some broad holes in it. Or maybe you notice holes in trees or logs. These are all bored, too.

But what causes all these objects to be so bored? In the case of the shell at the beach, the answer is predatory snails. Some snails – particularly moon snails – soften a clam’s shell by using a boring organ that produces hydrochloric acid, enzymes and other substances. Then the snail rasps the softened clam shell with a hard plate called a…

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Direct from the Genomics and Microbiology lab: A Scented Citizen Science Project!

July 10, 2015

This post is brought to you by Dr. Sarah Council, postdoctoral fellow for the Center for Science, Math & Technology Education at NC Central University in Durham, NC and in our own Nature Research Center.  Thank you Dr. Council!

Armpit group

Photo by Matt Zeher, NCMNS

Who hasn’t smelled themselves after a great run or an intense basketball game? You can thank your microbes for your body odor!  We want to learn more about them, so we recently hosted a multi-day sampling event at the Museum to explore the microbes of the human body and enlisted citizen scientists to help.

Microbes (single-celled organisms like bacteria, fungi, and archaea) make up over 90% of the cells on and in your body.  They benefit the human body by producing vitamins, breaking down our food, and even making us smell (1, 2).  Microbes located on your skin are what give us “body odor.”

The human skin microbiome (the microbial community on our outer surface), in particular the armpit microbiome, is composed of 4 to 5 types of bacteria, though the majority is made up of bacteria called Staphylococcus and Corynebacteria (3). Bacteria colonizing our armpits thrive from nutrients in our sweat and in turn produce the characteristic body odor smell (4). Knowing this important fact lead Dr. Julie Horvath’s team in the NRC Genomics and Microbiology lab to question how these bacteria affect our daily habits.

Armpit swabbing

Photo by Matt Zeher, NCMNS

For the Armpits, Microbes, and Odor project, we convinced 23 citizen scientists to let us sample their armpit microbes.  The goal: to better classify the microbes of the human armpit, understand the odor and other compounds the microbes produce, and rate the attractiveness of those odors.

On Day 1, we captured participant armpit microbiomes during a normal day, or the microbiome present as our subjects followed their usual hygiene routines.  From our participants, we sampled:

  • DNA (Deoxyribonucleic acid, the molecule responsible for coding cellular instructions for life)
  • Metabolites (molecules used as nutrients by living cells)
  • Volatiles (a type of metabolite that can be an odor)

We then asked participants to go without underarm product (antiperspirant and deodorant) for 3 days.  Antiperspirants act to physically block the excretion of sweat from glands under your arm. Deodorant products kill microbes with the use of alcohol-based solutions and mask the odor with fragrance.  Both products have a significant impact on the human armpit microbiome (5).

Our citizen scientists were allowed to shower normally, though we gave everyone a plethora of fragrance-free products, including shampoo, body wash, sunscreen, body lotion, and face lotion. Eliminating fragrance was important so we could capture a person’s natural smell. In addition, we gave participants cotton t-shirts laundered in fragrance-free detergent to wear as they slept for 3 nights. These t-shirts would soak up that natural smell.

Armpit shirt sniffing

Photo by Matt Zeher, NCMNS

On Day 4, we repeated the first day’s sampling, and participants turned in their T-shirts in a sealed plastic bag. But we didn’t stop there! Our participants and other citizen scientists then had the opportunity to participate in a “Speed Smelling” event in the NRC Daily Planet.  Emceed by our own Brian Malow, participants smelled the shirts worn by project participants as well as two unworn t-shirts washed in fragrance-free detergent. Over the course of an hour, each shirt was rated on overall smell, odor intensity and attractiveness by 20 smellers.  We also asked if the T-shirt had a specific smell and if participants could identify their own T-shirt.

Processing over 250 samples of DNA, metabolite and volatile samples will take some time but we do have preliminary results from our Speed Smelling event.  We learned that the top 3 most attractive t-shirts were worn by females and smelled floral and sweet.  To our surprise only one participant identified their own shirt.  One more interesting note was that a participant classified the unworn T-shirt as smelling like Boston Crème Pie!

Armpit Speed Smelling

Photo by Matt Zeher, NCMNS

We’re hard at work processing the samples from our citizen scientists, so stay tuned for further results connecting microbes, odor and attractiveness!

You can keep up-to-date on Dr. Council’s and Dr. Horvath’s work by following them on Twitter with hashtag #skinscent or by following @SarahCouncil and @NRCJulie.  You can also learn more about the lab and the armpit microbiome project at http://naturalsciences.org/nature-research-center/genomics-microbiology and http://armpits.yourwildlife.org/.

References:

(1) Turnbaugh PJ, Ley RE, Hamady M, Fraser-Liggett CM, Knight R, Gordon JI. The human microbiome project. Nature 2007 Oct 18;449(7164):804-810.

(2) Leyden JJ, McGinley KJ, Hölzle E, Labows JN, Kligman AM. The microbiology of the human axilla and its relationship to axillary odor. J Invest Dermatol 1981;77(5):413-416.

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