I can't answer the original question myself, but I came across a warning against feeding Indian sticks to mantids at this page on a UK site; http://www.small-life.co.uk/page2b.html . The relevant paragraph reads;
"The following are NOT suitable as mantid food because they can harm the mantid (either by poisoning or attacking it): ants, bees, wasps, spiders, woodlice, crickets, Indian stick insects, Peruvian stick insects"
I find it surprising to see Indian sticks (and crickets) in that list. I can't see Indian sticks putting up much of a fight, so the author must be suggesting they're toxic. Whether that health warning extends to frogs I'm afraid I've no idea. Maybe a PM to the author (Professor Phasmid!) of the page I linked to might shed more light.