How to block urls that request for robots.txt in lighttpd?

We have a dedicated development server which runs only test PHP applications on a public network.
We have setup session-based authentication for the site.

The issue we have is there are lots of 404s logged in access log for robots.txt.
So, We want to block/ignore these requests on the lighttpd to save some bandwidth.

How can we achieve this in lighttpd/1.4.31 ?