Do a practice ride first, just to clear out the spider webs. Consider it a dry run, which "doesn't count". Just forget about it once you finish it. And then go and enjoy the actual ride, predominantly spider-free! This is basically the same advice as cyccommute's one above, except you are basically using yourself to ride in front of you.

(BTW, has anyone tried using Garmin's "Virtual Partner" feature for that purpose?)