You need to throw away the feed.
The bugs are not dangerous to your chickens.. but they have spoiled the feed.. with they dropping and lava.. making it loose its nutrients... and the bugs poop and any dead or rotting bugs will be dangerous to the chickens.
Its best to only buy small quantities of feed so it can be consumed before any bugs start to breed in it.. also NEVER mix new feed with old.. like adding new feed to a feed bin that already has some food in it... otherwise you have no way of knowing how fresh the older stuff is.