keep a web
This can be done with flat spider webs. You know, the kind
with lines running outward from the center and covered with a
spiral which looks likes many evenly spaced circles. The spider
typically builds a new web each day. If no spider is seen on
the web, chances are it has been abandoned.
Spray the web with white or dark paint. Keep the spray
can at least a foot away to avoid damaging the web. Bring a
piece of paper up against the web. The wet paint will glue
the web to the paper. Cut the web free with a scissors.
Finally, spray the web and paper with clear varnish to
protect it.
If the paint was dark use light paper. If the paint was light
use dark paper. The web will show up better that way.