As I took one out, I noticed a strange, clear, gooey substance seeping out of it. I tried to wash it off, but it just danced around under the running water like rubber, still clinging to the peach.
After being slightly grossed out, I decided that maybe the rest of the fruit was still okay and cut around the offending substance. Then I found another pocket of that goo inside the peach. I cut around that too, and ate the rest of the peach which was sweet and slightly crunchy, by the way. Then I Googled. If it happens to be larva, I'm moderately confident that my stomach acids will take care of it.
Ontario freestone peaches for the win!