Dr. Kruipen called the parasites vertebrates, which the students read from his notes. They were later called bugs by the same students. Bugs are invertebrates. Then the student said, "They're vertebrates, they're not bugs."
From the door of the tent, Jane fires her rifle at point blank range, hitting her target standing just outside the tent, but the sound of her gun comes after her target is already hit.
"Vertebrate" was misspelled as "vertibrate" in Dr. Kruipen's notebook. Considering he was a research scientist, this is particularly egregious.