Why does the female pray mantis eat their mate

I'm just curious. it seems kind of pointless in my opinion. but seriously, why do they do that? is there some kind of scientific explanation? regardless, I'm glad I'm glad I'm not a pray mantis

If you read this 'Reproduction and life history' section of this article, it offers several hypotheses for this behaviour.
http://en.wikipedia.org/wiki/Praying_man…

Further, this article goes into more detail about sexual cannibalism...
http://en.wikipedia.org/wiki/Sexual_cann…

As a zoologist, I immediately thought of what is mentioned in this article - the female secures a meal after copulating with the male. In this strategy, the male has already succeeded in passing on his genes (the driving force of all life) and the female has benefited my having those genes that allow reproduction via the male sperm, so why not gain a meal in the process ?

I read that they do this to supply energy for the offspring. The male is "sacrificed" for the sake of increasing the survival rate of the offspring. The female may not be able to supply the necessary amount of nutrients to the developing offspring since the female gave birth and is initially weakened by this.

Before mating, she bites his head off, removing two of the three ganglia that serve as a brain. That way, the male has a one-track mind - - sex. Sort of like most teen-aged boys.