Barbarian observes:
The problem is, you seem to think God did #3 in a literal sense. If so, it hasn’t turned out the way you said it would.
Maybe there’s something wrong with this example?
We don’t even have any evidence that there was a “design.” God, being omnipotent, is a Creator, not a “designer.”
We do, however, know a great deal about the early living things, from which (as Pope Benedict said) other things have descened.
Fortunately, things like transitionals, genetics, molecular biology, and other sources of information can help. Would you like to learn about some of it?
Um…the evidence is that they did not. I’m going from memory here, but I believe that this is common among mantids that are ambush predators, not cursorial or generalist hunters. DNA phylogenies indicate ambush predation evolved once, from which a major radiation of species evolved. There are certainly examples of males being taken by the larger females in other families of mantids, but I don’t know of one in which decapitation is necessary. However, copulation is managed in (all?) insects from a ganglion lower in the body, and it’s likely that it would work well in any case where signals from the ganglia in the head were eliminated.
I need to read up a bit and see what’s out there. I’m not an entomologist, and my primary interest when I studied it, was in the area of medical entomology and parasitology. Don’t know of any mantids involved in that sort of thing.