Signs of Spring Update: May 7, 2001
Today's Report Includes:
Up, Up and Away!
The all-time favorite CHARLOTTE'S WEB ends in the springtime, as tiny spiderlings emerge from Charlotte's egg case. The gray orb spider called her egg sac her magnum opus, Latin for "great work." Charlotte told her friend Wilbur the pig that the egg sac held 514 eggs and would hatch in the spring. Her friend Wilbur the pig patiently waited, and this was his reward:
Wilbur was surprised and amazed when they hatched out, and even more surprised
and amazed a few days later when they did something he'd never imagined they would
do. One spring day, a warm draft of rising air blew softly through the barn cellar.
The baby spiders felt the warm updraft and one of Charlotte's children climbed to
the top of the fence. Wilbur was surprised to see the baby spider stand on its head
and point its spinnerets in the air. The spider let loose a cloud of fine silk that
formed a balloon. Wilbur was frantic when he saw the spider let go of the fence,
float into the air, and sail through the door with a "good-bye." At last
one little spider took time enough to stop and talk to Wilbur before making its balloon.
It was time for the baby spiders to set forth as aeronauts. They were going into
the world on a warm updraft to make webs for themselves. The air was soon filled
with tiny balloons, each balloon carrying a spider. That's our summary, but you'll
enjoy reading the whole chapter. You'll find the ballooning spiders in Chapter
XXII: A Warm Wind.
Floating on a Spring Breeze
CHARLOTTE'S WEB is fiction, but baby spiders really do balloon through the air, and they do it most in spring! Most baby spiders hatch when the weather gets warm, but a few hatch from their eggs during fall or winter. It's hard to notice that they've hatched, though, because they stay quietly inside the egg sac until spring. The first thing most kinds of spiderlings do after emerging from the egg sac is to spin a dragline and balloon away!
Baby spiders have no wings, but can fly as high as the highest-flying insects and birds! In fact, ballooning spiders often hit airplane windshields. How can a spider, with no wings, possibly get this high in the air? You'll find out by reading this week's report and helpful links that follow. Here's one:
Try This! Read Aloud
Get a copy of CHARLOTTE'S WEB and read Chapter XXII: A Warm Wind.
Spider silk is super strong; it's the strongest natural fiber known. Made of protein, it is produced in the spider's silk glands. Most species of spiders have five different kinds of glands, but seven different kinds have been discovered. Each type of spider silk gland produces a different kind of silk. Some make a liquid silk that dries outside the body. Others make sticky liquid silk that stays liquid and coats a dry thread of silk. Sometimes spiders produce a special silk that looks like a beaded necklace. They do this by pulling out a dry silk thread and coating it with wet, sticky silk. Then they let go of the silk with a snap. The jolt separates the liquid silk into a series of tiny balls of sticky silk. This kind of spider silk is especially useful for trapping jumping or flying insects.
Super Spinners and Wheels of Silk
Charlotte and her babies were orb weavers. It's easy to spot an orb weaver's web. Just look for a wheel of silk. The pattern in each web may be slightly different, but most of the webs are round. Orb means circle, and the round webs explain how these weavers got their name. Orb spiders weave beautiful, complicated webs, but they're all built to do the same thing: to trap flies, butterflies, grasshoppers, beetles, and other food. But even with eight eyes, orb weavers can't see very well. They make up for their blurry eyesight in another way.
Find out more about orb weavers and their wonderful webs here:
After reading about orb spiders, what ideas do you have to explain this?
Trapping Food Many Ways
Spiders use their webs to catch their prey, but they can't eat anything until it stops struggling. And spiders don't have strong mouthparts. They can swallow only liquids. A spider's mouthparts form a drinking straw that helps it swallow its food, but the problem is turning an insect's body into soup! Many spiders do this by "predigesting" their food. That is, they spit out stomach juices on the insect's tissues. The strong stomach acids not only do the killing, but they actually dissolve the insect. A large tarantula can liquefy and suck out a mouse, leaving nothing but a little pile of fur and bones, in 36 hours flat!
Ballooning Spiders and Other Aerial Plankton
People who study tiny bugs floating through the air call them "aeroplankton" or "aerial plankton." Dr. Jerome Rovner, one of the world's leading arachnologists (authorities on spiders), told Journey North: "Ballooning spiders indeed make up a large component of the aerial plankton. Charles Darwin noted a mass landing of spiders on THE BEAGLE when 200 miles off the coast of South America." Entomologists and people who study certain birds have long known that some tiny insects and spiders drift through the sky in the same way that plankton drifts in an ocean. Find out more, and learn how to observe ballooning spiders and other aerial plankton here:
Then come back and answer:
Watching a Spider
It may be a little difficult to watch spiders ballooning, but it isn't hard to observe spiders! Some even come into our houses to eat mosquitoes and other insects and tiny critters. Some people are allergic to spider bites, and even though most spiders virtually never bite unless seriously provoked, studying them closely involves a bit of a risk. But sometimes a classroom or home has a spider that stays in pretty much the same place all the time. Laura Erickson, a writer for Journey North, used to have a wolf spider that lived in her bathroom. Every morning when she or her husband took a shower, the spider crawled over to one wall near the shower to bask in the moisture. The rest of the time, the spider lived by Laura's houseplants, eating insects. Laura was happy because bugs never damaged her plants, and the spider seemed happy to have a safe and comfortable home. Laura was curious about why the spider loved that morning shower, and did some research. She'll tell us the answer next time, but in the meantime, see what YOU find out about the question:
What's in a Name? Discussion of Challenge Question #22
"Find a word in the dictionary that is related to Ephemeroptera. How do you think the Mayfly family got its name?"
The American Heritage Dictionary defines "Ephemeral" as: "1. Lasting for a brief time; short-lived; transitory. 2. Living or lasting only one day." Many mayflies live for two or three years as aquatic nymphs, but when they get their wings and emerge from the water as adults, most live for only a day or two.
Digesting the Information: Discussion of Challenge Question #23
"How do you think longer intestines help Yellow-rumped Warblers and Tree Swallows?
Plants have cell walls, which animals don't have. The cell walls are made of cellulose, and protect the nutritious food within the cells. Mammals that eat plants have sturdy teeth, sometimes complicated stomachs, and long intestines to break down those strong cell walls. Birds lack teeth, so no birds eat grass and only one species (the Hoatzin of South America) eats leaves. Most warblers and swallows eat only insects, which lack cell walls so are easy to digest. Yellow-rumped Warblers and Tree Swallows DO eat berries and some seeds when very hungry, and need longer intestines to help them break down the cell walls of this food.
Swallowing Signs of Spring: Discussion of Challenge Question #24
"Where do you think European and Asian Barn Swallows spend their winter?"
The answer: Africa.
Please Report "Signs of Spring" From Your Part of the World!
Your observations will be incorporated into "Signs of Spring" updates according to the schedule above. Thanks for sharing!
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The FINAL Signs of Spring Update Will be Posted on May 21, 2001.
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