Blow one balloon up to a very large size—as far as you can go without popping it—this will be the body of the spider. Mine is about one foot from the tied part of the balloon to the bottom.the yarn.
Blow one balloon up to a small size, holding it up to the large one so it looks like the size a head should be for the spider. Mine is about six inches from the tied part of the balloon to the bottom.
Squeeze some glue into a bowl. Pour in enough water to make a paste with the glue. You want the glue a little bit thinner so it is easier to work with. You'll probably have a ratio of 70:30 glue to water.
Dip a piece of yarn into the glue paste, and swirl it around to soak it
You can run the yarn through a fork that you hold on the edge of your bowl, or you can use your fingers to squeeze the excess glue out of the yarn. This will get excess glue off of the yarn
Using the balloon's tied tip as a good starting point, wrap the yarn around the tip to secure it in place.
Then, pull the yarn down one side of the balloon and up the other—back to the tip again—and wrap it to secure it.
Make more vertical strips around the balloon to use as a base
Continue doing that all over the balloon and place yarn sideways and diagonally, too—you'll end up glued yarn going every which way
Do the same for your other balloon. You'll want to let them dry overnight, resting them in the bowls or cups you have ready.
The next day, add second and third layers, adding more of a webbed look each time. Keep going until you're satisfied with the amount of yarn covering the balloons.
Let the yarn dry thoroughly - give them a couple of days - I know that's hard, but you want them to be stiff.
Finally, pop the balloons and pull out any remaining balloons - clean the extra glue pieces off of