Invertebrates

Discovering Diatomaceous Earth

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Diatoms as seen through a microscope. Note their stained glass window shapes and silica bodies (Photo: Wiki Commons).

To Use or Not to Use, That is The Question

As Spring infestations of pests, fleas, and insects begin, many homeowners are faced with how to control these critters, either in the home, garden, or even on pets. If you're like me, you'd rather stay away from chemicals all together. There are many different natural solutions out there for different organisms, but it's difficult to tell what works and what doesn't. In coming posts I'll explore some of these solutions, but I want to start with Diatomaceous earth.

Diatoms are a type of microscopic aquatic plankton or algae (2-200 micrometers in size). They are small photosynthetic plants.  We owe almost every other breath that we take to these numerous wee producers that are respiring in our lakes, rivers, and oceans. Their shells are made up of silica and calcium carbonate. In essence, they look like tiny stained glass windows.

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Pictures of diatoms under the microscope (Photo: Wiki Commons).

Their bodies are made like a gift box, with a top that slides over a bottom. When they reproduce, their two halves separate and then regenerate a new half. In the oceans, they are estimated to provide nearly 1/2 of all the primary food production for aquatic life! They've been around for a long time, all the way back to the Jurassic. Their glassy bodies have been floating around providing oxygen and food for millions of years. As these small organisms die, their glass bodies either sink to the bottom of the ocean or become sediment deposited on shorelines. When you look at sand under a microscope, you'll often see tiny grains of rock, but you'll also see the remains of diatoms. The main ingredient in making glass is silica, which is added in the form of sand. Guess who provided all those bits of silica? Diatoms!

Diatomaceous earth, or diatomite, is made up of the sedimentary deposit of fossilized diatoms deposited over millions of years.  They are usually whitish and abrasive feeling because of the nature of the silica, though the food grade kind may feel as soft as talc. It is very light because it has a high porosity and it is not combined with all the other heavy elements of rock and sand that are found in sedimentary sandstone.

Diatomaceous earth has been used in a variety of industrial settings, including for filtration, reinforcement of plastic, abrasion for tooth pastes, fillers for rubber and cat litter, and even stabilizing dynamite. One of its more common uses is as an insecticide.

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Diatomite from a mine in CA (Photo: AlishaV. Flicker)

As a pesticide, diatomaceous earth must be unheated or calcified (which is often done to increase its filtration value). Calcification burns or melts the silica, reducing its efficacy. If you were to look at diatomite under a microscope, you would see startling edges. These glassy edges are sharp as razors to invertebrates, but won't hurt humans or large animals. This is why it has been touted as a natural pest control. Before you get too excited though, let's really examine what it does to control all of these "pests."

Diatomaceous earth acts as a very strong cutting abrasive on the exoskeleton of invertebrates, including bed bugs, fleas, ticks, worms, slugs, and all six and eight legged insects. It is essentially the "death of a thousand cuts." Those cuts open up the organism to dehydration and infection within 24-48 hours, causing death. The other property of diatomaceous earth is that it is absorptive. It acts to dry out and desiccate the microorganisms that are cut by its sharp edges. So, how is this bad you ask? Diatomaceous earth is a generalist. When you apply it to your garden, you are in turn, not only killing the harmful slugs, grubs, roaches, silverfish, aphids, and thrips, but you're also killing all the beneficial insect life as well. This includes earthworms, pill bugs, ants, beetles, ladybugs, beneficial caterpillars, and more. This generalist approach is detrimental to the ecosystem, though perhaps less so than most chemicals. The other down-side to diatomaceous earth is that it loses its potency once it rains and the diatoms clump together. It has to be applied during dry days without rain.

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Beneficial jumping spiders may be negatively impacted by diatomaceous earth (Photo: Karen McDonald).

As with all pesticides, you have to consider the ramifications of using it in your garden or around your home. Yes, diatomaceous earth is mostly harmless to humans and pets (with a few exceptions of inhaling etc., and it is a controlled substance through the USDA), and yes, it can be quite effective in killing grubs and other garden pests. However, it's a generalist and like other chemicals, it kills everything indiscriminately. On a microscale, I can only imagine the "gory movie scenes" of what really goes on in the undergrowth and below ground once it is applied. I can picture the razor like edges cutting the microinvertebrates and their slow desiccating deaths. I have my own opinions, but everything has a cost and must be weighed. What do you think? Would you use it? Have you used it?

 

Ant Teaching Resources for Your Classroom

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An ant keeping his aphid "cows" safe. (Photo: K. McDonald)

Free and Low Cost Resources

As many of you know, I lead a double blogging life with my Citizen Science in the Classroom series on the umbrella citizen science site called SciStarter. If you haven't checked out their plethora of citizen science activities that you can get involved with, then head over to their site. In my series, I focus on specific citizen science projects and then help teachers figure out how to conduct those projects to meet grade specific, Next Generation and Common Core teaching standards. While writing my last post about a project called School of Ants, I was amazed at how little there is out there for teaching about ants. I had to do a great deal of digging to find teaching resources. But when I did, I found some great ones that I thought I'd share here. You can also check out my SciStarter blog post with Next Gen. and Common Core connections.

My favorite resource so far is Dr. Elanor's Book of Common Ants. This is a great free resource with wonderful illustrations, large ant pictures and close ups, and clear text. It's written for adults, but it's also kid friendly (4th-12th Grade). This book, along with a magnifying glass, is all you need to get yourself started with basic ant ID (or toss your kid outside with it and get them busy discovering on their own). I loved learning facts about pavement ants, winter ants, and the common little black ants called the "Odorous House Ant." Odorous house ants are the tiny little black sugar ants that come into the house. She suggests the "Squish-n-Sniff" for these guys because when you squish them, they smell good! This is how they got their names. How fun is that? If you are a naturalist at heart and want to learn more about ants, then this is the go-to resource.

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Dr. Elanor's book is an amazing resource. (Photo: Your Wildlife)

I found some other great teaching resources that might be helpful as well, such as :  ant lesson plans, MP3 interviews with ant researchers, free life cycle and anatomy worksheets, instructions for building an ant colony box, and more that come out of Arizona State University. If you haven't heard about their "Ask A Biologist" teaching resources, it's time to pop over to their pages (click here for their activity page). They have much more than just ant materials. You can find lesson plans, interviews, and worksheets, about plankton, space physiology, the nervous system, and more. It's worth visiting.

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Arizona State University has a great website on ants (Photo: ASU)

I also stumbled across a great video about ants on YouTube. It's called "ANTS-Natures Secret Power." It is a bit long to show in class (about an hour), but you could use segments or assign it as homework to the students.

I'd also like to suggest some of the following books:

DK Readers: Ant Antics. Lock. [2nd-4th] (used $.01)

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Are You an Ant? Allen and Humphries [K-5th] (used $1)

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The Fascinating World of Ants. Julivert et. Al. [2nd-5th] (used $.01)

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Journey to the Ants: A Story of Scientific Exploration. Holldobloer and Wilson. [Adult reading and reference] (used $.50)

EO Wils

There are many more books out there that are great, these are just a few. If you need magnifying glasses, ant farm kits, or other supplies, you can find resources on my "Nature Gifts and Teaching Supplies" page. The wonderful thing about ants is that they are everywhere and require very few materials to study and observe. Happy "anting" (this is actually a term used by birders when birds rub ants on their feathers for some unknown reason, but I think it applies here).

 

Tardigrades: Learning About Water Bears and Resources for Teaching

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Water bear in active state (Photo: Flicker, SaguartoNPS).

Tardigrades in Your Own Backyard!

One of my favorite invertebrates is the water bear or tardigrade. It is arguably the most extreme animal on Earth in the unassuming cute and cuddly form of a moss piglet with bear like claws. In this post I'm going to share with you some of the amazing natural history of tardigrades and some teaching resources that you can use for an indoor or outdoor classroom. If you're like me (and love exploring things like this) then you probably will also want to check these cool little guys out at home too, though you'll need a compound microscope to see them.

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Tardigrade in active state (Photo: Wiki commons)

Tardigrades belong to the phylum Tardigrada. They're aquatic invertebrates commonly found in the base of mosses and lichens; though they can also be found around the world, from the heights if the Himalayas to the depths of hot springs. They are known as extremophiles, meaning that they can live in places on Earth that most creatures couldn't handle. They can endure temperatures of absolute zero, pressure higher than that of the deepest oceans, radiation that would kill all other animals, and they can go without food or water for more than 10 years! Now you'd think a creature that can handle these extremes should be the large and flashy  but they're actually not much bigger to 1/2 a millimeter, about the size of the period made by a .5 mm pen.

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Leopard Slug Mating is Well....Strangely Beautiful

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Leopard slugs can be quite large, this is a beautiful specimen (Photo: Flicker Sharing, NorthDevonFarmer)

or "Ewwww, I Can't Look Away"

So once in a while I have to veer off track and bring you something completely different (much like my previous post on 50 foot cockroaches). Today I want to share with you something so gross and disgusting that it's almost beautiful (sort of like hairless cats and Shar pei dogs), leopard slug mating. Now for those of you that are gardeners you probably find leopard slugs (Limax maxiumus) a great nuisance that eats your vegetables and leaves slimy trails everywhere, but they are really much more complex (and a good cup of stale beer put out at night will take care of the problem).

Slugs 101

All slugs and snails are in the phylum Mollusca, along with squid, clams, and octopi. Slugs are gastropods, literally meaning "foot mouth". Leopard slugs have a noticeable mantle on their backs and in almost all species it's black spotted. They also have two optic tentacles with eye spots on the tips and two below them for feeding and tasting. Their anal opening is under the mantle (on the right side of the head) and they are hermaphrodites with both male and female genitalia.

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Anatomy of a slug (Photo: Wiki Commons)

Also on their mantle is a large hole or respiratory opening (called the pneumostome) that leads to lung-like tissue for respiration. Their respiratory opening opens and closes at regular intervals to prevent dehydration. Slugs glide along on a large muscular foot. The leading edge of the foot is called the "skirt."  Mucus is produced in glands on the "sole" of the foot. This mucus has specific pheromones that attract other slugs and also acts as a signal, trail marker, and travel lubricant. Underneath the smallest pair of tentacles is the rasping and chewing mouth part that are used to chew plants and vegetation.

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Identification Tips for Brown Spiders of the Eastern US

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A wolf spider carrying its egg sac. (Photo: Wiki commons)

Knowing What is and is Not A Brown Recluse or Wolf Spider

I'm often amazed at the number of times I've been outdoors with someone and when we see a brown spider immediately someone says, "Look, there's a wolf spider." I have to admit, I hate identifying "little brown jobs" or LBJs (a term we use commonly for brown sparrows when birding) because it's hard to find the fine distinctions between species, especially when the creatures are moving  or you're just skeezed out by the hairy eight legged creature crawling across your floor. However, it is important to understand that not all brown spiders are wolf spiders.

There are many different types of brown spiders and this blog post will help you begin to tell the difference between them. I'm going to write mostly about the spiders common to Eastern and mid-western North America, because this is my home range, but there is some overlap with western species.

A great starting place to learn spider ID and to become familiar with their body parts, names, and  the eye placement of spiders is on the website "Spider Identification Guide." I am particularly fond of their great graphic on the 25 different eye patterns you can find on spiders (I wonder if they make this in poster form?). Begin with the basics of spider anatomy on their website if you need a refresher. They also have a great guide for finding spiders by region and color. Check out their page on "Brown Spiders" for a quick browse of the diversity out there.

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An Introduction to the Teaching and The Citizen Science Website Journey North

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Journey North, a Citizen Science Website for Everyone

Journey North is a Citizen Science Website That Tracks Phenology (life cycle changes in plants and animals) and Seasonal Changes

Spring weather has briefly visited us this week, though the cold is coming back soon. But invariably we're seeing the first signs of Spring everywhere. This weekend the first osprey was spotted locally, geese are migrating, red-winged blackbirds are singing out their territories, and I heard a lone spring peeper. With thoughts of spring it's a good time to make you aware of a wonderful resource for citizen science. The website Journey North is designed as a tool for individuals and classrooms, as well as informal educators, to use for tracking seasonal changes and migrations. The term for tracking the seasonal life cycle changes of plants and animals is called phenology. This website provides the tools to track the phenology of robins, humming birds, whales, barn swallows, worms, first leaf-out, eagles, flowers blooming, caribou, whooping cranes, and so much more. They also specialize in providing tracking maps and information for recording seasonal changes in sunlight and weather.

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Examples of projects found on the Journey North website and "teaching" pages.

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Why There Are No Fifty Foot Cockroaches

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American Cockroach (Photo: Wiki Commons)

Sorry B-Flick Movie Lovers, 50 Foot Cockroaches Can't Really Exist!

I absolutely adore good B-flick movies, especially those with giant lizards, killer tarantulas, man-eating mole rats, and destructive turtles. However, the biologist in me always has a running commentary in the back of my head when I watch those films, I can't help it. So, just because it's useless fun knowledge, here's why it is impossible for fifty foot cockroaches to exist:

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Cockroach (Photo: Wiki Commons)

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An Introduction to Black Widow Spiders

Check Your Firewood Before Bringing It Inside

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Common North American Black Widow Spider, Female (L. Mactans)

Every year around this time I'm reminded that it's important to check firewood carefully before it comes inside. We keep our wood under a tarp outside near the house. Many different invertebrates, and even salamanders and other reptiles, will overwinter in a wood pile. Be sure to shake off the wood you bring inside because the warm interior of your house is a perfect place to "wake-up" and start crawling around if you're an insect!

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Camel Crickets 101

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Meet the Harmless Camel Cricket or Spricket

How many times have you gone down into the basement, into the back yard, or into your garage and found a hopping creature that looks like a spider and has the legs of a cricket? (usually this is followed by screaming or impolite words). This leaping creature is the camel cricket, a nocturnal insect in the order Orthoptera and the family Rhaphidophoridae (Rap-he-doe-fore-a day). They are light tan and brown, about 1-1 1/4" long, and they don't have wings (so no worries about flying). Camel crickets are related to cave crickets and occur across the US, all continents, and most islands. They like moist, dark, and damp environments which explains why you find them in garages and basements. The most common species here in the US is the Spotted camel cricket but researchers are finding that the Japanese camel cricket is also starting to invade our homes too.

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The Quietly Understated Roly Poly

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(Photo: Flicker, common use by Frank Carey)

One of the most common invertebrates you encounter when rolling over logs or looking under rocks are pill bugs, also called woodlice or roly polies. But have you ever really considered these harmless creatures? They lead a quiet and secret life, that of an aquatic invertebrate on land.

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