Month: November 2008 (Page 3 of 5)

Bug of the Week: Mud Dauber Wasp

Ever found a glob of mud stuck under the eaves or against the window sill of your home? This black and yellow beauty is an example of the type of wasp that probably put it there. This is a mud dauber wasp (Sceliphron).

mud dauber wasp

Notice her impossibly thin “waist.”

mud dauber wasp

Any idea what she is doing on this flower? No, she is not looking for nectar. Depending on the species, she was actually searching for caterpillars or grasshoppers, which she feeds to her young.

The adult wasp catches and stings the insects she uses as food. Then she carries them to her mud nest, where she stuffs them inside a mud tube she has created. She lays an egg on the processed prey. Then she carefully covers up the open end with more mud. Her offspring hatch from the egg inside the tube, and consume the insect or insects she has provided for them. After the larvae finish development and become adult wasps, they chew their way out and to fly off to make more mud nests.

Whenever I see a mud dauber wasp, I always think of the poignant poem called “The Digger Wasp” in Joyful Noise: Poems for Two Voices by Paul Fleischman, Eric Beddows (Illustrator). This wonderful set of poems about insects is written to be read by two people, although with practice one person easily manage it. Even the most apathetic, disinterested poetry non-fan will love these poems, because they are more like songs without music. In the poem I am referring to, the digger wasp mother provisions a nest for children she will never meet. Really makes you appreciate the hard work they are doing. That’s why I never destroy a mud dauber nest unless I know for certain it is empty.

Painted Lady Butterflies Migrating

It’s all about energy this morning.  I stepped outside to recharge my batteries and found painted lady butterflies everywhere. This time to year the painted ladies (Vanessa cardui) are migrating south, with rest stops in places like Phoenix where they can bask in the sun and drink lot’s of nectar from the pretty flowers everyone plants.

It’s in the low 50’s this morning, so the first butterflies I saw were basking on a wall with their wings directed to catch the sun. They are like mini-solar panels.

painted lady

Why are they basking? Insects bask in the sun to warm the flights muscles prior to flying.

I knew where there were some lantana plants in the sun, so I went to see what was going on there.

painted lady

More painted lady butterflies basking and drinking nectar. They weren’t cooperative at first, but after sitting still on a cold sidewalk for a few minutes, I was able to get a few good shots.

painted lady

painted lady

painted lady

Here’s one basking on a Texas sage.

painted lady

Seeing all these beautiful butterflies was a real charge for me. I hope other people notice them too.

If you are interested in learning more, or if you see painted ladies migrating and you’d like to participate in a study, check out the 2008 Vanessa Migration Project. Updated 2019:  The study is now at Iowa State

Weekend Science Fun: Why Do Apples and Pumpkins Float?

One question that has come up (pun intended) from previous posts in this blog is why do pumpkins and apples float? To answer this question, we first need to look at why things float in general.

Do you still have your bin of water? Let’s try floating a few more things.

People have been wondering why things float since olden times. According to legends the ancient Greek, Archimedes, conducted experiments to test why things float or sink. Supposedly he figured it all out while sitting in the bathtub. Our modern interpretation is called Archimedes’ Principle.  It states that a body floating in a fluid is supported (or buoyed up) by a force equal to the weight of the fluid it displaces.

Let’s choose water as our fluid. Do you know how much a cubic centimeter of water weighs? How about a gallon?

A cubic centimeter of water weighs 1 gram by definition. A gallon of water (at a given temperature of 4 degrees C) weighs 8.34 pounds. So, in order to float, an item that weighs 1 gram must displace more than a cubic centimeter of water. An item that weighs 8.34 pounds must displace more than a gallon of water to float.

To test this, obtain a piece of modeling clay. Shape it into roughly a cubic centimeter. See if it will float. It will probably look something like this:

sunk

(Clay at the bottom).

Now, flatten out the same piece of clay and make a boat shape. A flat bottom with a lip around the edge works well. Place it onto the surface of the water. It should displace a lot more water this time and float. Although the weight of the clay didn’t change, the amount of water displaced did change.

float

Have you tried floating a can of diet soda versus a can of regular soda? Both are the same size and shape, will they both act the same when placed in water?

Here’s a silent video demonstration.

Why don’t the two identical objects act the same way? According to the box at the bottom of this How Stuff Works page, diet soda has less sweeteners added, so it actually weighs slightly less for the same volume than regular soda. Because they are both mostly water, that slight change is enough to allow diet soda to float. Cool!

Apples and pumpkins are not solid. The pumpkin has a large hollow inside. Both weigh less than the amount of water they displace, and thus they float.

Try floating pumpkin seeds. What about apple seeds? Do they float?

We found that pumpkin seeds floated, but apple seeds did not. The pumpkin seeds are flat and displace an amount of water roughly equal to their size. On the other hand, apple seeds are compact and round. They displace little water. They don’t have to be very heavy to sink.

A few years ago, our family participated in a contest to build a working boat out of cardboard. We started by investigating various boat designs and materials by floating models in a tub. We learned a lot about sinking and floating. You might want to make some paper boats and try them yourself.

Enjoy!

Instructions to make a Classic paper boat

Another cool design for a paper boat that works well.

Edit: check out this video of a huge pumpkin made into a boat.

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