Good question! The real reason spiders do not get stuck in their own webs is pretty simple. A spider web is able to catch small insects because it has small sticky droplets on the silk threads. But there is still a lot of silk thread that does not have sticky droplets on it. Spiders are clever enough to step on the parts of the web that are not sticky, but when insects fly at very high speeds they cannot see where they are going, and they land on the sticky bits.
(published on 09/03/07)