So what i want is the a black ladybug to be eaten when the backdrop is white and a white ladybug to be eaten when the backdrop is black by a mouse when that happens i want the ladybug sprite or its clones that are touched by the mouse to disappear. How would i go about this. Tried the when touching black and white ladyback block but doesnt work.
Thank for your help.

There are some bugs with some of the touching blocks at the moment.

http://scratch.mit.edu/discuss/topic/30868/

You can work round that by adding a Show block just before each test.

Other than that, if you have already made a start on the project, why not share it so others can give you specific advice.

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    Simplify
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