Ah, ok, this is normally called a rollover. A nice way to do this is with what's called a "sprite" image.
Basically, you have one image with a button at the top and the bee below it. Perhaps place this image as a background image on a <button> element. The trick it only to show a part of the image at a time. So, without hovering, you just see the text part of the image, and then wen you hover, the bee part of the image jumps into view.
Here is an article about how to do it. Have a go at this and come back if you have any problems.
A List Apart: Articles: CSS Sprites: Image Slicing’s Kiss of Death
CSS Sprites: What They Are, Why They're Cool, and How To Use Them | CSS-Tricks