The Filmy Dome

Teacher's Story

IKE bubbles cut in half, these delicate domes catch the light rays and separate them like a prism into waves of rainbow colors. One of these domes is usually about the size of an ordinary bowl, and is suspended with the opening on the lower side. It is held in place by many guy-lines which attach it to surrounding objects. Above a filmy dome are always stretched many crisscrossed threads for some distance up. These are for the purpose of hindering the flight of insects, so that they will fall into the web. The little spider, which always hangs, back downward, just below the center of the dome, rushes to its prey from the lower side, pulls it through the meshes of the web, and feeds upon it. But any remains of the insect or pieces of sticks or leaves which may drop upon the web, it carefully cuts out and drops to the ground, mending the hole very neatly.

A filmy-dome web with its maker. Photo by J. H. Comstock.

Method—On a sunny day in late summer or early autumn, while walking along woodland paths, the careful observer is sure to see suspended among the bushes or in the tops of weeds, or among dead branches of young hemlocks, the filmy dome webs. They are about as large as a small bowl, and usually so delicate that they cannot be seen unless the sun shines upon them; they are likely to be exquisitely iridescent under the sun's rays. Such a dome may be studied by a class or by the pupils individually.

3. Where does the spider stay? Is the spider large and heavy, or small and delicate?

4. What does the spider do if an insect becomes entangled in its web?

5. Throw a bit of stick or leaf upon a filmy dome web, and note what becomes of it.