A couple of thoughts about "toxic prey".
A large insect like an eastern lubber emits enough poison through its spiracles to kill the occasional small bird. Birds will also sometimes become ill after eating Monarch butterflies, though some species are apparently becoming resistant to the toxin in the perennial war between attackers and defenders (some ground squirrels are reputed to be immune to rattlesnake bites).
Toxic or noxious insects, though, tend not to kill other insects or spiders partly, perhaps, because spiders and predatory insects tend to eat their prey bit by bit instead of swallowing it whole like a bird does. However, the taste is often so distasteful (yes I know) that the insect predator hurls and avoids similar insects in the future.
Now here's the problem. A naive predator will snatch a noxious (evil tasting) insect and kill it before realizing its mistake (this has been described as social altruism by some theorists
) but will thereafter avoid specimens of the same species. How does it do that? It uses warning (aposematic) coloration, involving a combination of all or two of the colors, black, red and yellow. You learned this stuff in high school, right? Sometimes, two noxious insects occurring in the same environment and showing the same warning coloration are said to exhibit "Mullerian" mimicry. If there are two insects in the same environment (subject to the same predators) with the same aposematic coloration and one is noxious (like a wasp) and one is not, like a hover fly) then they are said to demonstrate Batesian mimicry with the yummy insect being protected by its resemblance to a a noxious one.
The problem with these well-established theories is that it is not enough for an insect to be noxious, it has to be the right color as well (many predators, such as mantids can detect color better than overall shape, and I really don't want to argue this at length), so to be successful, an insect has to be either noxious and appropriately colored or yummy and appropriately colored to match a noxious insect in its environment. It is true that a given insect's' colors vary, and a combination of noxiousness and the right color over time is a reasonable proposition, but I am a little troubled about the all-embracing nature of the theory. A notorious example is provided by the Viceroy butterfly, whose range overlaps that of the noxious Monarch and was long considered an example of Batesian mimicry. Then it was discovered that the Viceroy
was toxic, and instead of disproving the theory, it merely made the Viceroy a Mullerian mimic.; it's a theory that would probably tee off Sir Karl Popper.
Well, enough of that. As Joe mentions, a number of grasshoppers will vomit up part of their crop's contents when startled. It isn't nearly as dangerous as the toxin from the eastern lubber's toxin excreted from the spiracles, but it does contain irritants sufficient to make a predator reluctant to try again. This is the famed "tobacco juice spit."
So don't worry unduly about prey insects poisoning your mantids. Noxious insects like the Monarch are eaten without problem by mantids, and if a mantis does eat anything it doesn't like.
And Likebugs, I have fed hundreds of bees to mantids without one ever being stung. I've been stung a couple of times, though!
