Absoluite statements, my friend, will get you every time. Check Superfreak's copy of the Prete book, last para on p.313 and over to the next page. Since we are never sure of our charges' nutritional needs it is a sound practice to give them a variety of foods.
Young Alex, of course, is talking nonsense about crickets being generally available to ambush predators on flowers. Not just flower mantids, but even mantids like Asians and Giant Shields do very well on bees, and Tucker and I usually collect about 16 every morning. I have noticed that if I feed a couple of crickets at about 0900, they are often still alive and well when I check around noon, but a bee is frequently taken within seconds of being placed in the enclosure. This does not speak to one's nutritional value over the other, of course, but it does suggest that a variety of mantids have a predeliction for flying prey.
I know that you can obtain crix in Sidney, which must be particularly useful at this time of the year, but I do recommend that you eschew any store where you see crix exposed to mould and rampant nasties!