Ann -- the spider is outside, right and very tiny? It is very possible that the spider is eating other incests that are too small for you to even see!

We live in an old house and consequently have lots of spiders -- especially at certain times of the year. I am always cleaning out cobwebs and don't think I have ever seen a fly caught in one. And trust me -- the spiders live long enough to reproduce!

This may be a time to assume that mother (nature) knows best and the spider is catching appropriate food.

(The webs are beautiful, aren't they. Especially when it rains! What I DON'T like are the webballs (???) in which they lay eggs.!!)