Of course in large numbers within a home they must be dealt with but in the garden and our larger Eco-system they are indeed our friends.
Their name is derived from the fact that they lay there eggs within a host. Many of these hosts are Aphids or Caterpillars that destroy our crops.
Below are some videos that show and explain this process.
THESE VIDEOS ARE GRAPHIC DEPICTIONS OF NATURE PLEASE TAKE THIS INTO CONSIDERATION BEFORE VIEWING THEM