The main joke isn't really all that funny, nor is it very timely (the incident at the University of Florida was more than three months ago).
It seems in panel one that Grimmy has walked up to Ralph's front door to ask why he is holding the imprisoned fly high up in the air at arm's length. In panel two, Ralph is for some reason now to the left of Grimmy. And in panel three, he has returned to standing on his doorstep.
At first, I was a little confused about why the characters had swapped places. Then I thought that the author, whose name I can't make out from the illegible scribble he left, must have done this in order to get the dialogue to flow in the correct order without having to cross the speech bubbles. The picture we see in the second panel must have been drawn as seen from the other side of the characters. It's confusing to have the characters flipping back and forth like this, though. Personally, I would have left the characters in their original positions, and simply put the cat's speech bubble above the dog's; the reader would read the bubbles correctly this way. Switching their dialogue doesn't seem to upset the comic too much, either:
Also, why didn't Ralph rescue any of those other flies in the background? There's about twenty flies hovering around the bug zapper, seconds away from flying into instant death. He rescued only one.