If you want to take a flag out of the mouth of a mantis you have to make a formal request first. Mantises don't like to just give things away, and they're kind of mean so if you try to steal the flag it will probably bite you. So make a formal, polite request if you want it.
After you request the mantis give you its flag it shocks (しょく) you by actually spitting it out of its mouth at your feet. You didn't think your request would work, or even if the mantis understood human speech, but it shocked you by doing exactly what you asked!