 FACT: In the last scene where the male bug is struck by the train,  you see it struggling to hold onto the front of the train for a  while. It manages to hang in there for a little while before being  pulled under and splattered everywhere. But when Dr Susan looks  around the corner, after the bug is killed, she sees parts of the  bug just meters away from where she was hiding. The bug should be  further down the tracks, because it was dragged for ages before  going under.