It's very normal to get some flies, gnats or ants from time to time in almost every shipment we recieve in about 10% of our shipments.  What this typically comes from is when the rock is in it's curring process on the islands where it's spread down with fresh ocean water, some flies, gnats or ants may get into the boxes while being boxed out in the open. 

Especially with flies, maybe only a couple flies or gnats make it into the box and will lay eggs on the rock as they are attracted to the liverock smell out of the water and then comes the average two day shipping time to the United States where it's forwarded directly from us to our customers.  As a direct tran shipper, we don't remove and clean off all the rock which is how you are recieving it at such a low price.  The pet stores who buy from us throughout the U.S. and Internationally alike, simply rinse off the rock, soak it in a bucket of saltwater and it's perfectly clean and ready for sale or use.

Ants will sometimes even crawl up into the boxes on the beach where they are trying to move into cool damp shady areas by the swarms.  Once again, a simple rinse and dip and they're all gone.

In no way will any of these things harm your rock or will it arrive in any less quality than the boxes that don't have this problem.  For the general public, it just looks bad.