Recently our family was watching the movie "A Bug's Life" and my 9 year old daughter asked me "Can a Praying Mantis and a Butterfly have babies together?"  I saw the post on this site about spiders NOT cross-breeding but nothing on insects. 


Is this genetically possible?  If not, why not?

Please help. 

Marian

Nope, not possible.  At least, not to my knowledge.

As for the why not, short answer is they are different orders of species, any member of a species can breed with any other member of the species, but not with any organism outside of the species. That is we look and see whether any naturally occuring hybrids are ever seen, if not then we can classify them as different species. Mechanisms stopping a mantis and butterfly hybridising will be behaviour (they simply do not recognise each other as potential mates), gamete incompatibility (the sperm and egg do not recognise each other and so do not fuse), and genetic incompatibility, these are two orders of organisms which evolved apart tens of millions of years ago, over which time natural selection has altered their genes and bodies considerably. Basically their genes are so different to each other that they cannot work together to create a functioning organism, the genes from the butterfly are trying to make a butterfly and vice versa with the mantis, the result most likely if the genes were somehow brought together in the lab would be a completely inert cell. The more recent in evolutionary history two organisms are, the better their chances of being able to make hybrids together, for instance lions and tigers or donkeys and zebras, where the differences between them are not so great and the chances that the genes can work together are greater.